AFAICT that's the default for jazz jams, at least, though there's some variation.
There's one I usually don't attend as I'll be lucky to get one go in the first set and one in the second, then get back to bed near midnight for an 06:00 alarm and 90+ minute commute the next day.
Another, where I am the house player, it's extremely rare for another bassist to appear. When they have they have brought their own bass guitar and amp and we have then alternated two tunes on and two off between us. If they wanted to use my upright I would be reluctant to let them play more than a couple of tunes during the night.
My least favourite jam (> 20 years ago now) involved turning up early to set up, then helping the drummer and keyboard player, and playing for the first 30-40 mins or so. At that point other bassists would turn up and demand to use my bass and/or amp, supported by the MC because "you've already played for a while", and this would go on until the end of the night when I would get out last and struggle to find a taxi.