I had a bike fitting a couple of years ago and since then have been cycling a lot more than previously.

How often should one be refit? I'm comfortable, but the fitter gave me a more upright configuration because of his assessment of my flexibility. I feel I could change that back, but the rest (seat height/position) seems fine . . .

Fit can be a constantly moving target for some folks. Those of us who live where there is winter often lose some flexibility until we can get more miles in during the spring, and some folks have pain issues that require constant tweaks. Eddy Merckx famously readjusted his saddle height during races, and was always having new frames built to try new geometries.

When I started riding a road bike, I had a short (quill) stem that was raised up to its limit. As I put in more miles, I switched to longer stems and lowered them as my flexibility improved. Sounds like you might be ready for a re-fit, whether you do it at a shop or tweak the setup at home.

Change something, ride with it like that for a while, see how that feels.