What are the benefits to remaining in the the military beyond 20 years?

The military by its very nature demands extraordinary sacrifices that are often at the expense of family members. So it is natural as you grow older to reevaluate the existing balance between the service and the personal needs, desires and expectations. IMO it is a zero some game. To fully devote yourself to the military mission means that your personal life must give up things that would demand your time and attention. Likewise to fully devote yourself to personal/family matters, your military effort must by definition be less. You can't optimize both. Each person and family must determine if the tradeoffs required are worth the positive aspects of staying in.

Then separate from family considerations are your own professional goals and satisfaction. It's possible as you move up in rank and authority that you feel like the future holds mostly jobs that aren't ones that give you the most satisfaction. Generally speaking, the higher up you go, the more your time is spent in front of a computer rather than in front of soldiers. You may feel removed from the very things that you loved about being in the Army. Or maybe you may feel like the future holds more of the same rather than offering a new set of challenges. So you have to look at what you expect to be doing in those years after 20 and determine if that appeals to you or not.

I experienced the same situation myself. After battalion command, I was selected to attend the Army War College. But due to my personal situation I decided that it would be best for my family if I got out rather than stay in. So I declined attendance to the War College and consideration for promotion to COL and got out instead. My friends thought I was nuts. But it was the best decision I ever made.

But To me it was the right time to rebalance the scale so to speak. For others it may not be. But the fact we all face is that somewhere between 20-30 years your career will end whether you want it to or not. So you are only delaying the inevitable. You're going to transition out anyway, so 20 is a good time to really take a good look at the personal costs associated with "squeezing out" a few more years, so to speak.

I am retiring in a few weeks... I don't know that I was ever a lifer, per se...but I am starting to see what I have been giving up all this time - mainly that I am tired of moving every 24 months, but not sure where, and not really my choice.
I want some control, I want to plant some roots and join a community....

In about three weeks I will be put out to pasture by the Air Force at my 30 year point because that is the limit put on enlisted careers. I stayed past 20 and would gladly continue to serve because of the incredible men and women I got to serve with, the satisfaction of knowing I was doing something that had significant impact, and because I felt I was needed.

Yes, the Air Force I am leaving is considerably different from the one I joined and the challenges we face in uniform now are greater because of the political climate and demands of our society, but it is still my Air Force and I will miss the daily camaraderie and sense of family.