I think the AOG is a fantastic organization. They pay for a lot of things that people think are paid by the academy/tax payers. Things like many of the trips that the cadets get to go on during their 4 years. The AOG is the "Alumni Organization" of academy graduates. They definitely deserve your support.
Having said that; a lot of things can change for you in the next couple years. 1) Don't make it through BCT; 2) Realize the Academy isn't for you; 3) Get separated because of academic issues; etc... With that in mind, I usually suggest to cadets, that they wait until commitment. (Start of your 3rd year). The price is the same; you'll be making full pay by then and will be able to pay the whole thing at one time; and you'll be pretty positive by then that you'll be staying in and graduating. It's not that much money, but why support something if you aren't part of it. So; whether you pay the AOG all of it now, in 2 years, monthly payments, etc... they are getting the same amount of money from you. I just suggest you want until the fall of the start of your 3rd year. Just my $0.20484853 (Inflation). Mike....