Google's return window is getting extended once again: Android users can now request a refund within two hours after they've downloaded an app or game.
http://www.theverge.com/2014/9/10/6132761/android-app-return-window-extended-to-two-hours
I still remember when it used to be 24 hours. Didn't use it much but 15 minutes was just useless, especially with games that have extra content downloaded on the first run.