So we're an instumental power trio-no vocals. The tunes are pretty much blues based with the odd meter change, key change, whatever. There's really no verse chorus type formula- it's more just a sequence of riffs/parts through all our songs. Average length is 8 mins with very little repetition of parts throughout the tune.
We're all seasoned players and not beginners but have only really been jamming since january. But it reeeeeaaaaaaallllly pisses me off when we can play a tune perfectly one week and the next it's like everyone has forgotten how the tune goes.
I almost had an "episode" last night at jam and had the camera been rolling i may have had some footage to contribute to the "bands fighting on stage" thread happening at the moment. But we talked it out like oprah and things are cool now.
But my question is this: Is this common for other bands? how long does it take for you guys to work a new tune into your set? couple weeks? months?

I hear you. Sometimes people really forget that stuff. To me, that stuff should be fairly easy to remember, or those people probably aren't cut out for it. I mean, there's fairly well known bands that have members in different towns, yet they get together and they can remember the songs no problem, or with a minimum of refreshment. One of my issues about being in various bands throughout the years is trying to ascertain how much time to put in with working with specific people, before it's apparent that they're just not cut out for it. You can ultimately spend alot of time showing guys riffs and song parts, only to have them forget it completely the next week or be badly out of tune or whatever. Some guys are really enthusiastic about the material, but it's--like you say--they press reset on themselves only to make the next jam frustrating in having to re-learn things. One guy that i'd worked with would need to listen to the recordings, minus everything but the drums--I did that for his own requests in the beginning, but after awhile, he was forgetting things and rehearsing to the song in a different key, and walking up with his own version that was completely different than the actual recorded song. I'm not sure if there's any real way to overcome that.....some players just naturally have their own deficiencies and i'm not really sure if more practice is the answer. There's always a certain level of compromise that's involved, but it depends on what level of compromise can be mutually agreed on.....i've never been one to shy away from a beer or three during a jam, but some guys would get pretty hammered or stoned out of their skull, and they didn't remember things the next jam.

i really dont want to play with any other guys and i dont give a shit if your high/drunk as long as you can still play well. And let's be honest, i'm not in this for the money, chicks or fame- just wanna keep it low key and fun. But i'm not willing to write/play half-assed shit at the same time.
The bass player's my bro (literally) and fuck was i close to giving him an out if he wanted one. But one thing's for sure- they got the message that you really do have to do homework outside the jam space if you want it to stick.

Yes. Practice is what you do at home individually, rehearsal is what you do at the jam room collectively.

Hmm. It probably takes my band a few months to be ready to introduce a new song into the set list. Sometimes more. Not becuase everyone's forgetting how it goes, really just because we only get to practice 1-2 times a week and one of our guitar players travels for work on a pretty regular basis which can nix practice for a week at a time. We spend a lot of time crafting songs, and debating about which parts we should use and where. So, we usually need to record a song in the rehearsal room so that everyone can practice at home and get the structure down, becuase we make so many changes during the writing process. Playing live shows slows down the writing process because we need to spend rehearsal time practicing the set list and if we don't have the new one down pretty solid we're not going to try it at a show.

Once we've gotten past the point where we're making changes though, we usually only need a couple practices to get a song into decent shape.