I recently finished developing a simple news app for the iPhone. I wanted to reduce the overhead of the app as much as possible and I wanted a refresh feature but I didn't want the user to have the ability to receive news updates from my service at his will. So I made the cache only expire after 15 minutes. When the user clicks the refresh button within 15 minutes of a previous click it actually does nothing, but display an activity indicator for 2 hard coded seconds. This isn't for critical news updates. Just very slow niche news updates. It's my most recent version of a placebo button.