diff --git a/MapControl/Shared/MapBase.cs b/MapControl/Shared/MapBase.cs
index f901530c..fa4d1652 100644
--- a/MapControl/Shared/MapBase.cs
+++ b/MapControl/Shared/MapBase.cs
@@ -31,8 +31,6 @@ namespace MapControl
     /// </summary>
     public partial class MapBase : MapPanel
     {
-        private const double MaximumZoomLevel = 22d;
-
         public static TimeSpan ImageFadeDuration { get; set; } = TimeSpan.FromSeconds(0.1);
 
         public static readonly DependencyProperty MapLayerProperty = DependencyProperty.Register(
@@ -321,6 +319,7 @@ namespace MapControl
                 if (rotation != 0d)
                 {
                     var heading = (((Heading + rotation) % 360d) + 360d) % 360d;
+
                     SetValueInternal(HeadingProperty, heading);
                     SetValueInternal(TargetHeadingProperty, heading);
                 }
@@ -328,6 +327,7 @@ namespace MapControl
                 if (scale != 1d)
                 {
                     var zoomLevel = Math.Min(Math.Max(ZoomLevel + Math.Log(scale, 2d), MinZoomLevel), MaxZoomLevel);
+
                     SetValueInternal(ZoomLevelProperty, zoomLevel);
                     SetValueInternal(TargetZoomLevelProperty, zoomLevel);
                 }
@@ -437,17 +437,16 @@ namespace MapControl
 
         private void AdjustCenterProperty(DependencyProperty property, ref Location center)
         {
-            if (center == null)
-            {
-                center = new Location();
-                SetValueInternal(property, center);
-            }
-            else if (center.Longitude < -180d || center.Longitude > 180d ||
+            if (center == null ||
+                center.Longitude < -180d || center.Longitude > 180d ||
                 center.Latitude < -MapProjection.MaxLatitude || center.Latitude > MapProjection.MaxLatitude)
             {
-                center = new Location(
-                    Math.Min(Math.Max(center.Latitude, -MapProjection.MaxLatitude), MapProjection.MaxLatitude),
-                    Location.NormalizeLongitude(center.Longitude));
+                center = (center == null)
+                    ? new Location()
+                    : new Location(
+                        Math.Min(Math.Max(center.Latitude, -MapProjection.MaxLatitude), MapProjection.MaxLatitude),
+                        Location.NormalizeLongitude(center.Longitude));
+
                 SetValueInternal(property, center);
             }
         }
@@ -519,6 +518,7 @@ namespace MapControl
             if (minZoomLevel < 0d || minZoomLevel > MaxZoomLevel)
             {
                 minZoomLevel = Math.Min(Math.Max(minZoomLevel, 0d), MaxZoomLevel);
+
                 SetValueInternal(MinZoomLevelProperty, minZoomLevel);
             }
 
@@ -530,9 +530,10 @@ namespace MapControl
 
         private void MaxZoomLevelPropertyChanged(double maxZoomLevel)
         {
-            if (maxZoomLevel < MinZoomLevel || maxZoomLevel > MaximumZoomLevel)
+            if (maxZoomLevel < MinZoomLevel)
             {
-                maxZoomLevel = Math.Min(Math.Max(maxZoomLevel, MinZoomLevel), MaximumZoomLevel);
+                maxZoomLevel = MinZoomLevel;
+
                 SetValueInternal(MaxZoomLevelProperty, maxZoomLevel);
             }
 
@@ -547,6 +548,7 @@ namespace MapControl
             if (zoomLevel < MinZoomLevel || zoomLevel > MaxZoomLevel)
             {
                 zoomLevel = Math.Min(Math.Max(zoomLevel, MinZoomLevel), MaxZoomLevel);
+
                 SetValueInternal(property, zoomLevel);
             }
         }
@@ -611,6 +613,7 @@ namespace MapControl
             if (heading < 0d || heading > 360d)
             {
                 heading = ((heading % 360d) + 360d) % 360d;
+
                 SetValueInternal(property, heading);
             }
         }
@@ -684,7 +687,9 @@ namespace MapControl
         private void SetValueInternal(DependencyProperty property, object value)
         {
             internalPropertyChange = true;
+
             SetValue(property, value);
+
             internalPropertyChange = false;
         }
 
diff --git a/MapControl/Shared/TileImageLoader.cs b/MapControl/Shared/TileImageLoader.cs
index f51315cd..bb43b610 100644
--- a/MapControl/Shared/TileImageLoader.cs
+++ b/MapControl/Shared/TileImageLoader.cs
@@ -30,11 +30,10 @@ namespace MapControl
         public static TimeSpan DefaultCacheExpiration { get; set; } = TimeSpan.FromDays(1);
 
         /// <summary>
-        /// Format string for creating cache keys from the cacheName argument passed to LoadTilesAsync,
-        /// the ZoomLevel, XIndex, and Y properties of a Tile, and the image file extension.
-        /// The default value is "{0}/{1}/{2}/{3}{4}".
+        /// Maximum expiration time for cached tile images. A transmitted expiration time
+        /// that exceeds this value is ignored. The default value is ten days.
         /// </summary>
-        public static string CacheKeyFormat { get; set; } = "{0}/{1}/{2}/{3}{4}";
+        public static TimeSpan MaxCacheExpiration { get; set; } = TimeSpan.FromDays(10);
 
 
         private class TileQueue : ConcurrentStack<Tile>
@@ -51,7 +50,7 @@ namespace MapControl
         }
 
         private readonly TileQueue tileQueue = new TileQueue();
-        private Func<Tile, Task> loadTile;
+        private Func<Tile, Task> loadTileFunc;
         private int taskCount;
 
         /// <summary>
@@ -72,11 +71,11 @@ namespace MapControl
                     tileSource.UriFormat.StartsWith("http") &&
                     !string.IsNullOrEmpty(cacheName))
                 {
-                    loadTile = tile => LoadCachedTileAsync(tile, tileSource, cacheName);
+                    loadTileFunc = tile => LoadCachedTileAsync(tile, tileSource, cacheName);
                 }
                 else
                 {
-                    loadTile = tile => LoadTileAsync(tile, tileSource);
+                    loadTileFunc = tile => LoadTileAsync(tile, tileSource);
                 }
 
                 tileQueue.Enqueue(tiles);
@@ -98,7 +97,7 @@ namespace MapControl
 
                 try
                 {
-                     await loadTile(tile).ConfigureAwait(false);
+                    await loadTileFunc(tile).ConfigureAwait(false);
                 }
                 catch (Exception ex)
                 {
@@ -122,7 +121,7 @@ namespace MapControl
                     extension = ".jpg";
                 }
 
-                var cacheKey = string.Format(CacheKeyFormat, cacheName, tile.ZoomLevel, tile.XIndex, tile.Y, extension);
+                var cacheKey = string.Format("{0}/{1}/{2}/{3}{4}", cacheName, tile.ZoomLevel, tile.XIndex, tile.Y, extension);
 
                 await LoadCachedTileAsync(tile, uri, cacheKey).ConfigureAwait(false);
             }
@@ -130,7 +129,16 @@ namespace MapControl
 
         private static DateTime GetExpiration(TimeSpan? maxAge)
         {
-            return DateTime.UtcNow.Add(maxAge ?? DefaultCacheExpiration);
+            if (!maxAge.HasValue)
+            {
+                maxAge = DefaultCacheExpiration;
+            }
+            else if (maxAge.Value > MaxCacheExpiration)
+            {
+                maxAge = MaxCacheExpiration;
+            }
+
+            return DateTime.UtcNow.Add(maxAge.Value);
         }
     }
 }
diff --git a/MapControl/WPF/ImageFileCache.WPF.cs b/MapControl/WPF/ImageFileCache.WPF.cs
index fb528554..2d9016d1 100644
--- a/MapControl/WPF/ImageFileCache.WPF.cs
+++ b/MapControl/WPF/ImageFileCache.WPF.cs
@@ -169,7 +169,9 @@ namespace MapControl.Caching
 
             string path;
 
-            if (imageCacheItem.Buffer != null && imageCacheItem.Buffer.Length > 0 && (path = GetPath(key)) != null)
+            if (imageCacheItem.Buffer != null &&
+                imageCacheItem.Buffer.Length > 0 &&
+                (path = GetPath(key)) != null)
             {
                 try
                 {
@@ -282,7 +284,7 @@ namespace MapControl.Caching
         {
             try
             {
-                return Path.Combine(rootDirectory, Path.Combine(key.Split('\\', '/', ',', ':', ';')));
+                return Path.Combine(rootDirectory, Path.Combine(key.Split('/', ':', ';', ',')));
             }
             catch (Exception ex)
             {
@@ -294,14 +296,15 @@ namespace MapControl.Caching
 
         private async Task CleanRootDirectory()
         {
-            var deletedFileCount = 0;
-
             foreach (var dir in new DirectoryInfo(rootDirectory).EnumerateDirectories())
             {
-                deletedFileCount += await CleanDirectory(dir).ConfigureAwait(false);
-            }
+                var deletedFileCount = await CleanDirectory(dir).ConfigureAwait(false);
 
-            Debug.WriteLine("ImageFileCache: Cleaned {0} files in {1}", deletedFileCount, rootDirectory);
+                if (deletedFileCount > 0)
+                {
+                    Debug.WriteLine("ImageFileCache: Cleaned {0} files in {1}", deletedFileCount, dir);
+                }
+            }
         }
 
         private static async Task<int> CleanDirectory(DirectoryInfo directory)