I think the timer is fine. 60 minutes before (1.0) was kinda punishing, especially since there was less responsiveness over all, a 3 minute Weakness, and no shortcuts to take you 1/3 of the way through the dungeon each time.

90 minutes is a LONG play session for me. Typically, will try to get up every 30-40 minutes to stretch, grab a cup of water, hug a cactus, or a punch a squirrel in the face. I also think it's kinda like, "Hey, this party, these tactics, this gear, isn't going to work," effect.

I realize the privilege of regrouping with the same folks doesn't exist in duty finder, much the way finding other folks on the server can.