There's always the,"working for half pay" thing. And before some as swipe points out that doesn't include BAH--yes, I know.
Still, at 20 you get the check to cover basic bills, then you can pursue something else you like for 10 years while getting a paycheck and possibly a new retirement plan on top of your existing one.
To each his own. If you stay past 20, stay because you enjoy it. The money you can get anywhere. The flying's probably done at 20, unless you have serious E time, so you just have to REALLY like the big green (or blue) gun club.