Well it depends on who it is, you might have a better chance this year with NIN. We saw (two years ago) Bright Eyes right before Coldplay. I went up to the front of the sound/camera rig right after Bright Eyes was done (and it was packed). People left to goto the bathroom whatever, and my gf did that while I went to the front of the rig. That is a great place to stand for a show. So I would not leave in between QOTSA and NIN, I would work your way up after QOTSA.