Is there an app that is preferrably free that will shut off (not just mute the phone as I don't want Pandora sucking bandwitdh all night) that will shut off Pandora or spotify after a certain amount of time?
Not free, but you probably can use Taskerto do this. I use Pocket Casts to listen to podcasts, and have a Tasker profile set up:
3 Contexts: Shake left-right; app Pocket Cast running; Not Docked Car
2 Tasks: Notify (turn LED on, title "Sleep"); Wait 12 minutes, then Pause Simulate Media Button, then Notify Cancel title "Sleep"
Net effect is that I can shake the phone left then right, and Pocket Cast will behave as if the Pause button on a headset were pushed 12 minutes later. I used the notification LED so I could tell whether Sleep had been activated when the screen is off.
I'm guessing Pandora would observe the headphone pause function; if it does, this profile should work for you.
Yes tasker is the key but I prefer llama because its free and its awesome. Actually its location based profile app but it can be used for your condition.
There is a condition called "time between", add that condition and choose "kill application" for its action. Add your desired time and application