Now, I know the achievement says: No Pausing. But, I had a thought. Pressing the guide button does not enter the pause menu, and changes nothing in the RB2 game. Is it possible to pause like this and still get the achievement? I haven't tried it, and it would be pointless to redo the whole setlist and try it once, but does anyone actually know if it may be possible?

No, I'm 99% sure that Harmonix released something that basically said you cannot stop the note charts or the "in-between-song-cut-scenes" in any way.  The guide button stops both of those, so it would negate you from getting the achievement.

Guide disables the achievement. Kind of an obvious answer if you ask me. Pee before the setlist then go to town! I did this achievement already, was a sweaty six hours.

You have to do it on expert though right Vinchenzo? How the fuck did you get through GGHT?

"You have to do it on expert though right Vinchenzo? How the fuck did you get through GGHT?"

Uggh, I did the endless setlist on expert vocals and didn't pause. Then comes Rob the Prez-o-dent (which is approximately song #70 out of 84) which I fail because that guy sings like Christopher Walken talks. I don't see why that song isn't all talky. No problems before that song and no problems after it either. I was pissed.

There are two different types of achievements that come from the Endless Setlist: The Bladder of Steel and the Difficulty Achievements. The Difficulty Achievements are just "Beat The Endless Setlist on (Insert Difficulty Here)". For these, you can pause/fail a song and still get the achievement. The Bladder of Steel (Which is what you are talking about) is the one where you can not stop in any form (Failing/Pausing, and yes the Guide Button counts as pausing).

"Uggh, I did the endless setlist on expert vocals and didn't pause. Then comes Rob the Prez-o-dent (which is approximately song #70 out of 84) which I fail because that guy sings like Christopher Walken talks. I don't see why that song isn't all talky. No problems before that song and no problems after it either. I was pissed."