I think I would like to stay full 20 but I want to take it one contract at a time.
To get the terminology correct, and I guess the mindset too, officers do not have "contracts" like our enlisted folks do when they enlist and re-enlist. You are commissioned, have an associated minimum active duty service requirement, and you just keep going unless you quit after that or are forced out by failure to promote. Your "contract" for an aviation officer is wings + 8 years, though those waters have become muddied in the last year. So roughly 10 years depending on how long flight school takes. You can choose to leave after that, but you don't ever sign up again, you just stay to retirement or resign your commission (or for some of us, transfer the commission over to the navy reserves)