Right! So every quarter or maybe once a month max then.

Yeah, whatever works for you. When I was at a place that did regular 1:1s, my manager always stressed that they're for me, not for the company, and if I want to change the frequency of time I should just let them know. Not sure about your company culture, but if you're already experienced, I can't imagine your boss would be unhappy if you said "you know, I don't need so much guidance, let's have less 1:1 meetings". Assuming most of the communication happens in regular team meetings, which seems healthy.

This is exactly what I do. For the first month or so I recommend weekly 1:1s, just to make sure they are adapting well and getting the things they need. There are a lot of internal systems to navigate, tons of folks they should get to know, etc. But once they are a bit "settled" the frequency is really up to them with a minimum of once a quarter. I've been in companies before where managers only met with their employees for things like this once a year at review time! This often led to resentment and morale problems when performance reviews didn't align with employee expectations and by the time they find out it's too late to course correct. You must keep folks appraised of how well they are meeting expectations both good and bad. The "annual review" should contain no surprises for anyone.