The Slushbusters meet twice a month. We decided long ago that we couldn't possibly critique a submission from each of us at every meeting, so we capped it at five people's submissions. Each meeting, someone has to "opt out." This is never a problem. Someone always has something they want to work on some more, or is out of town or has some other reason for not submitting pages. Only once in a great while have we had to choose who would opt out. We originally made it all official, deciding ahead of time who would submit for the next meeting, but so rarely is it a problem that we don't even talk about it anymore.
The other thing we don't talk about is that we have never not had something to critique. Any time I have to opt out, the day of the upcoming meeting creeps closer, and I find myself wondering if we'll have anyone's work to discuss at all. We always do. This, I believe, is one of the small miracles of our group. We complement one another in so many ways. One person's weakness is another person's strength and all. But it even happens in timing. One person's dry spell is another's flood of work. Amazing.
I hope I didn't just jinx us by bringing it up.