the meetup is pretty informal. we tend to kind of drop in/out. some people like to get the character pics and might pop in a little later, some people like to get to their corral right away and leave sooner. I'd say that the bulk of us arrive somewhere around 30min after the reunion area opens, and most everyone is gone 30min after the corrals open. Some of us get to the meetup and chat for a little bit, then pop over to gearcheck (we are right by the entrance to gearcheck) and then maybe pop back over to say hello to anyone who may have just arrived. there are no rules!
Looking at this past MW's thread, it appears we did a group pic at around 4am on 10k day, and then mostly wandered off to corrals shortly after that (at least DH and I did, I can't speak for the others.)
It looks like we mostly split up by 4am for the HM on Saturday (where we all got drenched in the downpour)
And on Sunday I was in my corral by 330, after stopping at the meetup for probably around 20min.