I had Pats tickets from 92 to 12 (I think). Once I turned 21 and was legal for the football season (in 95) I don't think I watched one game completely sober - and I only missed 1 game (vs Tenn in 98 for my mother's wake) in that time. I openly admit this. Almost everyone in the parking lots is/was sh#tfaced to some degree during the pre game tailgate, game, post game tailgate.
It was completely normal for my friends and I (numbering from 4 to 20 depending on size of the group going together to the game and whether or not we took the winnebago) to start drinking at 8:30 am for a 1 pm kick and drink straight through the post game. Personally I would estimate between 20-30 beers if not more for myself.
It wasn't just us. Anyone who's had season tickets has seen debauchery in the parking lots. I distinctly remember the Buffalo game in 07. Beautiful day - maybe 75 degrees out. Postgame tailgate before we turned back the clocks so the sun was still out. Some guys in our tailgate started playing beer pong with the females next to us and one thing led to another and some girls were in various stages of undress right there in the parking lot for all to see. Cripes, one dude used to put up a stripper pole and had a DJ set up post game. He would give shots to any girl that danced on the poll. This was back when Gillette first opened - maybe 02-05 season when we used to park kind of in front of the stadium coming from heading south on Rt 1.
I was in a big brawl post game after Atlanta blew out the Pats in 98. Right there in Lot A. Had a spiral fracture in my left fibia to show for it. Stuff was crazy....
Maybe its different now, but I remember most people being hammered at the games...