How often are vaginal exams performed during labour?

My labour was pretty fast. I checked into hospital at 5pm, and my baby was out by 10pm. The first check was done at the waiting ward to determine if I was really in labour. At first, it was 3cm, then the next time they checked 10 minutes later, it was already 5cm, so they wheeled me to the ward. The next time they checked about an hour later, I was 9cm dilated. So it really depends.