It depends on what you want. If you want to be close to the band, yes, you have to be there many hours ahead of time to get a good spot. Last time some even slept there! If you are a small person, or just hate being knocked around, I'd say, keep to the back or get there early enough to get up front. If you don't have the rail to hold onto, you will be smooshed, elbowed, knocked around and other unpleasant things. Some people do this because they are assholes, some do it because they are so wasted they don't know what they're doing, some are just so excited and jumping around they don't realize they are being pushy. So it all depends on what you are willing to put up with.
If you have a good spot and don't want to lose it DON'T go to the bathroom! Sure, you might get your place back, but you might not. Someone might take it, or the crowd might be so thick you will never make it back up front. No drinks at least 2 hours before showtime!