For fun... I stop playing when I stop having fun. I have been known to walk out of expensive scenarios, because the fun wasn't there.
I have a gearhead streak, and it helps pay for my playing.
Plus I have a bunch of friends that play, and the comraderie is great.
Oh, and I use paintball as a substitute for real physical workout. Of course it must be working... I lost 85 pounds a few years ago, and kept all but 10 of it off. Now to lose the remaining 100, and I will be the same weight I was back in high school