You can leave the Air Force, but will the Air Force leave you.
I did 19 years in the RAF before being offered a good financial inducement to leave early, in '74 (too many chiefs). I was then fortunate enough to have a second career lasting 20 years before retiring at 56, although I did continue working part-time.
Whenever I look back on my life, as one does, I have vivid memories of quite a few aspects of my RAF career, which I mostly enjoyed and many of the people I served with. However my civilian job, which could be quite demanding, was just that, a job and I seldom think about it at all.
I must admit that reading PPRuNE does jog the memory somewhat. In fact since I've joined I've made contact with a couple of guys from wayback.