30 minutes is perfect, enough for people to take a break after a wipe, or go take a quick bathroom or smoke break. and if you accidentally exceed the time or something comes up your out of game. also stops people from trying to talk to an AFK person.

Considering how this helps them also analyze true concurrent connections and helps keep resources dedicated to area's that need it. I would say its a perfect number. that helps both the playerbase and the game's resource management equally.