You just gotta gauge the crowd for the band you're watching vs. the distance to the next band you wanna see. Stay as long as you can at the current one and then look for the least densely packed way to get out. I usually give myself 5/10 minutes in between to move. You can still jam as you walk away, just be polite and considerate when moving through the people who are still jamming away happily in their spots. Go around them in a zig zag pattern as unobtrusively as possible. Also, don't expect to get super close for every set. I'd rather see more sets farther back then fewer at the front.
Depends on the act for sure, and the feeling of the crowd can vary from front to back, but you can usually still jump stages and get fairly decent spots for most stuff. But it's all in what your priorities are. This year going to two weekends does change the amount of stage jumping I did do weekend one know I still have next weekend.