Correct. If you're running more than one dyno in an app, however, there are no 'timeouts'.

If you're trying to maximize your free dyno usage, however, you might want to use the 'heroku scheduler' addon, and have it ping your app once every 10 minutes to keep it 'awake'.

Yeah, it's killed after a timeout and restarted when a new request comes in. Which is why when you revisit an old Heroku app it takes a long time to load.

You can keep a single free Dyno "awake" by hitting it with a request at least once per hour. If you use New Relic the built in availability monitoring will do the trick and otherwise Scheduler should work. For more info:

https://devcenter.heroku.com/articles/dynos#dyno-idling