It sounds like the standard caching is not good enough because you have no control over what will be cached and for how long. The easiest way for solving this is by creating your own caching meganism by overriding the NSURLCache. You can find some documentation about that at http://nshipster.com/nsurlcache/ and a sample at http://github.com/evermeer/EVURLCache That sample even let you use a pre populated cache that can be included in your app install.
