Oh man, I agree that sometimes jam sessions are boring, but I've heard many that are not.

You do you, but for me, some jams are just sublime, the longer the better in those cases.

For example -https://youtu.be/kAUs187IT4I

Norman Granz' Jam Session #2 (1953)
Alto Saxophone – Benny Carter, Charlie Parker, Johnny Hodges
Bass – Ray Brown
Drums – J.C. Heard
Guitar – Barney Kessel
Piano – Oscar Peterson
Tenor Saxophone – Ben Webster, Flip Phillips
Trumpet – Charlie Shavers

Real improv, real gone, man! :)

You’ve never been to a bluegrass jam, then. That’s a party, and there’re plenty of songs to go along with the tunes, too. The solos are short and go off, and then you’re back at it. A song or tune only lasts so long and there’s always movement to keep it alive(which is why I didn’t say old time fiddle music since it’s also very repetitive).

Jazz jams, as someone who swing dances, are generally incredibly meh. The core audience take themselves too seriously to create a fun atmosphere, and the solos all last waaay to long. They play for themselves, often to the point where even the band is disconnected from itself. My friend once played a recording of her friends at a jam for us to practice to and it was so bad that they weren’t even in time with eachother.

Go to your local bluegrass jam and relax. Playing music with others is really important.