drinking on the job?

here's the situation:
in honor of the state fair (yay!) my building at work is having a mini-fair this afternoon in the lobby and parking lot. we will be fed fair food of the corn dog/nachos/funnel cake variety, have midway games, and...wait for it...beer. everyone in the building has been issued 2, count 'em, 2 drink tickets for FREE BEER. fair fun starts at 4 this afternoon (crash it if you know where i work) and, after passing out the drink tickets this morning, i watched the fine art of bartering and bribery in action. several people, who shall remain nameless, have amassed quite a collection of drink tickets.
now here's my question: how many beers can a person ingest in 2 hours, at work, in the middle of the afternoon, without leaving a bad impression of co-workers? because realistically there are going to be people on every floor who don't drink/leave early/etc who i'm sure have shared the wealth with the drink-friendly, so a lot of people are not going to be tied to the 2 drink limit. we'll see.