You can use any bank you want. USAA and armed forces bank are two of the biggies. Many people use armed forces bank initially; mainly because they have a branch office right there at the academy. Some keep this bank for their entire career. Many however will change banks later on to USAA. If you decide to get the 0.5% interest $35,000 loan that is offered to cadets, that is offered through USAA and you'd have to open an account with them. They aren't right there on the academy, but they are local in colorado springs. Many people keep this bank. USAA is also much larger in their services. I.e. Car insurance, investments, etc... "Look both of them up in a google search".
But you can use any bank that you prefer. But the air force and academy require that you have "Direct Deposit", so you must have a bank. Armed forces bank is the easiest initially. Especially if you're young and new to having a bank account, debit card, etc... They are right there to help you. Do I recommend them? Yes. Again; only for convenience. That's who my son started with. Plus; there's an Armed Forces Bank here at home at the air force base. So; if we wanted to add some money to my son's bank account, we could do it without sending him money. But now that he's a junior, and decided to take the $35,000 loan, (To invest), he opened an account with USAA. He changed his direct deposit to them. He'll probably cancel his account with Armed Forces Bank eventually; but there's nothing to say you can't have more than one bank account. I have 3.
And yes, you can keep a bank forever. When I came into the air force, there really wasn't USAA or Armed Forces Bank nearby. But USAA has been around for a very long time. Then again; we got paid with paychecks initially too. But when I got stationed at Kirtland AFB in albuquerque, I opened up a bank account with Sandia Area Federal Credit Union. My military pay, and NOW My Retired pay, has been going there for more than 30 years. So yes, many people keep their banks forever. But that's only if you like them. "We love our bank.... Yes we do.... We love our bank...." LOL!!! Sorry; that's a stupid commercial. Anyway; there's no law. You can change banks any time you want; or have as many banks as you want.
But I do suggest for the noob at the academy; start with armed forces bank. They are local for the cadets on base, and are very convenient. Once there, and a year or two later, you'll know if you want to change to USAA; keep them both; or get a totally different bank.
Get good grades & Have fun FTW. Who needs sleep?
