I've found there's another afternoon benefit. If I'm standing in the afternoons and struggling to stay awake, that's a really good push to take a short nap.

When I'm sitting in the afternoons it's easier to push myself and skip the nap, which actually results in worse productivity and me feeling worse the rest of the day. It's harder to skip a nap with a standing desk because it's harder to tolerate being sleepy when standing.

YMMV based on if afternoon power naps work for you or not.