Perhaps it would get boring, and surely you don't get the notoriety and money of a starter, but it seems to me that being a backup QB is not a bad gig. Generally you are not a cripple by the time you are 40, for instance. I'm sure your competitive nature makes it frustrating to stand and watch, but if they keep in mind that they are essentially judged to be one of the top 100 QB's in the world, that is not so bad.