2 hours appears to be right according to this website below...
http://milwaukee.brewers.mlb.com/mil/ba ... ctions.jspDepending on what you are there to do my recommendations are
to get there at least an hour before the gates open if you want to
have the area you want. Personally I have tailgated in the preferred
parking Miller lot just east of the stadium and enjoyed it the most.
If you are able to park close to the Sausage Haus you have a short
walk to the stadium and plenty of clean bathrooms to use in that building.
If you want to play bags or washers or whatever you have plenty of
room for that as well right there. Depends on if you want to spend that
kind of coin to park. They don't generally hurry you out after the game so
conceivably you could spend 6 or 7 hours there if you didn't go into the game
but I don't think they open up 5 hours before the game.