Further to this I think the "right" session length is also somewhat dependent on the Domme......both her skill set and her playspace/equioment etc.

My longest pro session was years ago with Mistress Brianna of DC She had a full basement filled with custom things like cages, crosses, an isolation box, bondage chairs, a bondage wheel, overhead attachment points as well as countless racks and shelves of restraints, hoods, gags, electro boxes, CBT stuff, dozens of CP implements and other gear. It was as is she'd gone to major equipment suppliers like Fetters and Mr S and ordered one of everything!

Multiple positions, lots of variety and 6 hours flew by.

Having a great Domme who you connect with matters tremendously but she also needs enough gear to work with if you are doing more than an hour or two.