Approximately how much should the PI and postdoc or grad student attend meetings together versus separately?
I think the together part is obvious and should be the majority of the time. The PI is supposed to be introducing the trainee around.
But flying solo can be great for independence.
The big shottes *have* to talk to you if the PI isn't at the meeting. So I'd definitely be okay with a handful of meetings where the trainee is there without the PI.
Making it habitual, however, is MentorMalpractice.