22 hours isnt too bad so long as you get good sleep the day before. just be sure to drink plenty of water, have snacks with in reach and take short breaks between dungeons.
a lot of people are going 24 hours. longer than that then Might be a concern.
only thing i would suggest is end an hour earlier on Tuesday or start an hour later Wed so the group can actually get a full 8 hours of sleep. people are not mechagnomes and thus cant go into sleep mode at the drop of a hat epic.