I try to run these as casually as possible on no specific timeline. I find regular, standardized 1:1s to be a dystopian experience.

The way most of my 1:1 calls initiate usually starts with someone else on the team expressing a bad mood about something and me doing a quick check in on teams.

I find that happy or otherwise productive employees will either reach out actively on their own, or not require this sort of interaction in the first place.