I misread something about recommendations for guys who shave their head:

It also might be worth your while to let [your hair] sprout up every so often, to ensure that [it’s] still as dense as you remember. Because the last thing you might want is to decide to grow it out again, only to realize that you’ve got no choice left.

I thought they meant that shaving it might damage your scalp, but a reread seems to say that your scalp will continue to evolve even if you’re shaving it–which makes sense. It’s not a timestop in terms of the aging process, where you’ll still have the same number of hairs or that they’ll be in the same color as when you last saw them grown out.

That said, as I started shaving my head because of a growing bald spot and thinning elsewhere, I think I am already in the “no choice left” camp. It’s been a while since I could credibly pretend I still have the hairline of my youth, and nobody is ever fooled if you try.