My wife and I went 3:00Pm several weeks ago on a Friday. Her passport was stamped around 3:30Pm and mine was stamped around 3:45Pm. I was the last one of that day.
By the way, I was not trying to play the bottom line of timing on that day. Actually, we just got our notices around 12:00noon from the lawyer and knowing the stamp should be on Friday only before 4:00Pm, so we went home to pick up passport and take photoes....and arrive there 3:00Pm with red face. So, if you have time try to get there ealier specially before long weekend. Good luck!