I know with 2-3 I was the one who asked to be checked, and I was definitely in transition. It was at that point where 'I hope this isn't lasting much longer', and I was something like 9 cm with the second and 7 1/2 with the third. My third was posterior, otherwise I'm pretty darn sure he would have been even quicker (a little bit longer labor than my second even because of it).
With the fourth, I'd had 2-3 painful contractions (not long but noticable--we knew I was on the fast side already so though they were 8-10 minutes apart still we figured we'd call). So, we called the midwife while I was on the toilet, she was in a meeting so she said she'd finish it and come over. I got off the toilet, and leaned over against the towel hooks and had one really hard contraction. I was thinking "crud, I hope I don't have to do this for another hour or two".....(that should have been my clue) well, of course, he was born around 5 minutes later with DH catching. Woops. I can only hope this one will be that quick! LOL I had like 5 painful contractions, and they weren't even that close together.
So, hey, after this past one who needs to be checked! Though I probably was complete and would have never guessed it.