PM me your email address and I'll send you an Excel spreadsheet I built. I used three companies I think I'd like to work for, DAL, FedEx and SWA. The I compared the pay staying active duty until 20 and then making the move, and leaving when my commitment is up and going reserves and airline.

Making the assumption that you do the bare minimum as a reservist, and stay on the smallest airframe at each airline, and don't upgrade to left seat until 10 years, the total pay earned at age 60 is more across the board leaving early than staying until 20, and that's using the conservative upgrade times on the smallest equipment. That also assumes nothing but current pay scales, as well as the 2010 DFAS table. YMMV but you can change the inputs of the spread sheet to recalculate if you'd like a copy of it.