In my experience, it hasn't been a great thing to go with a plan for doing so many rounds. Usually in long sparring sessions emotions run over, technique suffers and injuries occur. There are pros in our gym that go 15 or 16 rounds with 30 second breaks (particularly when the outclass their partners). I have seen guys getting ready for ten rounders go 6 rounds with 2 different high level guys (that was one minute rests). With your experience I would say 8 rounds is enough to get great conditioning and salvage some technique but even that is a lot. If you feel good during a given session you could always decide to go another round or two but I think you get diminishing returns after a point. This is a boxing opinion, I only did MMA for a short time and didn't love it but I got more gassed in that than I did boxing. Sparring at an outside gym is almost always rougher than sparring at home. I suggest more frequent, shorter sessions.