Two days is good, but if you go on vintage festival race weekend, you need 2 days for that by itself.
There's really just TOO MUCH to see and do, if you also intend to spend time visiting with friends. People who have tried will tell you, there's no way to do it ALL.
-In the pits, checking out race bikes being worked on & talking to racers
-helping out in the pits (endless opportunities)
-checking out the pit lane as grid groups come and go, to see & hear the bikes
-watching the actual races
-going through the swap meet (even longer if you are buying or selling)
-seeing the bike shows (even longer if you show a bike)
-seeing interesting bikes parked from one end of the faclility to the other
-riding the tram, just taking it all in
-checking out the auction (longer if bidding and/or selling)
-sampling the food
-watching the airshow and seeing other static exhibits
-riding the nearby area if you came on a bike
-riding the track, if you pay for the guest rider lap(s)
-visiting in the campground with friends, and making new acquaintances
-meeting and talking to Mr. Barber & his staff
Two full days in the museum will give you a much more enjoyable time than just the typical half-day visit; plus you need that much time to get good photos and read the "poop sheets" on each of the interesting bikes on display at any given time.
