I have noted that when the iPhone OS receives a push notification, it considers that a user action to click on the action button as a "response" to the push notification for some indefinite period of time. If the user lets the push notification sit on screen for a number of seconds, or lets the phone go to sleep, the phone no longer considers the users action as a response to the push notification itself, and therefore does not launch the corresponding app.
So my question is... does anyone know what the precise definition from the iPhone OS is as to how long the phone considers a push notification response to be corresponding to the push? Sorry, I can't find a great way to phrase this question, but I hope it makes sense. I'm guessing its something like 20 seconds from my testing, but I don't see this specifically documented anywhere.