In general, how long would you say a regular interview dinner (not a happy hour) lasts? Sometimes programs give the end time (ie, 6-8pm), but if not (ie, starts at 7pm), when can I expect it to be done most likely? one hour? two hours?
They are not necessary. So if you are exhausted just sleep. We here at the IM forum do recommend going to them all things otherwise being equal because 1) free food, usual good to excellent, and 2) you'll get a feel for who the people are at the program and if they are all a bunch of weirdos or not.
Drink *A* beer or glass of wine if you like but don't go for seconds and avoid hitting on any women there (*even if* they are hawt and *even if* they start it)
Basically use the dinners to YOUR advantage. Don't over think them.
But they take you out to lunch at that cool chineese restaurant after the interview. I kinda liked doing that instead of the typical style of taking a plate of food to eat while listening to noon conference. Changes up the pace a bit