                     keys.remove(key)
                     continue
                 }
-                if object.estimatedExpiration.isPast {
+                if object.isExpired {
                     storage.removeObject(forKey: nsKey)
                     keys.remove(key)
                 }

            guard let object = storage.object(forKey: key as NSString) else {
                return nil
            }
            if object.expired {
                return nil
            }
            object.extendExpiration(extendingExpiration)

            }
        }
        
        var isExpired: Bool {
            return estimatedExpiration.isPast
        }
    }
