diff --git a/imagekit/conf.py b/imagekit/conf.py
index e99cfcd..d183f00 100644
--- a/imagekit/conf.py
+++ b/imagekit/conf.py
@@ -7,7 +7,7 @@ class ImageKitConf(AppConf):
     CACHE_BACKEND = None
     CACHE_DIR = 'CACHE/images'
     CACHE_PREFIX = 'imagekit:'
-    DEFAULT_IMAGE_CACHE_STRATEGY = 'imagekit.imagecache.strategies.Pessimistic'
+    DEFAULT_IMAGE_CACHE_STRATEGY = 'imagekit.imagecache.strategies.JustInTime'
 
     def configure_cache_backend(self, value):
         if value is None:
diff --git a/imagekit/imagecache/strategies.py b/imagekit/imagecache/strategies.py
index e44929a..f134673 100644
--- a/imagekit/imagecache/strategies.py
+++ b/imagekit/imagecache/strategies.py
@@ -2,26 +2,21 @@ from .actions import validate_now, clear_now
 from ..utils import get_singleton
 
 
-class Pessimistic(object):
+class JustInTime(object):
     """
-    A caching strategy that validates the file every time it's accessed.
+    A caching strategy that validates the file right before it's needed.
 
     """
 
     def on_accessed(self, file):
         validate_now(file)
 
-    def on_source_deleted(self, file):
-        clear_now(file)
-
-    def on_source_changed(self, file):
-        validate_now(file)
-
 
 class Optimistic(object):
     """
-    A caching strategy that validates when the source file changes and assumes
-    that the cached file will persist.
+    A caching strategy that acts immediately when the source file chages and
+    assumes that the cache files will not be removed (i.e. doesn't revalidate
+    on access).
 
     """