My band gets along fairly well. No one is a douche and we're all kind of on the same page style-wise and musicanship-wise. Now that we've been together for a couple years though we're having one problem over and over again - too many songs. EVERYone in the band comes in with songs or 'ideas for songs' and while that is fun when we're in the practice space, when it comes time to making up a setlist for gigs, we get into arguments over what songs to include. Like I said, we're all fairly reasonable about this, but you can still tell that people are getting pissed off, or getting their feelings hurt if this song or that one doesn't make the list. How do people deal with this particular band problem? - co-writer.
Too many great songs to chose from. wow... that sounds like a fairly good problem to have. The most important thing is that you sound like a fairly democratic band made up of reasonable people. So what to do?
So someone in the band brings in a song they've written or a idea for a song and you all give him/her the floor to run it down. Then everyone decides whether or not they like it, or what they might add to it. So far so good... but you're right, if you've got a bunch of creative people constantly bringing in new songs, you can build up quite a backlog after a couple of years.
It almost sounds like you're all maybe too polite with each other - not wanting to hurt each other's feelings or stifle someone's creative ideas. That's great... but sometimes a little more stringent honesty is called for. So you have to ask yourself IS this new song at least as good as the other stuff you're already playing - or is it hopefully WAY better than the other songs? That is what you should all be shooting for... not just turning in another "ok" song but instead creating something so awesome that everyone else jumps up and says "We GOTTA play this song at our next gig."
So a new song has to get put to a REAL vote by the band members, and if a majority likes it then the trick is to find a slot for it in your set list. THIS of course raises more questions for me. You said you've been together for a couple years, but I have no idea how often your band actually plays out. Are you steady-gigging every week? ...or, like most new bands, do you go months between shows? This matters because if you're booking tons of shows then it should be easy to slip new tunes into the rotation for at least one 'try-out' ...but if gigs are more rare for you then the set-list is a much bigger deal... I'm guessing since your band is so cooperative, that you all somehow make a committee decision on your set list... That might work, or you might take turns letting ONE person make up the whole set list. Other options: You could each pick your top ten songs (in order) and then tabulate the results and play only the songs that got the most votes... However you decide to do it, it is critical that afterwards the band discusses what songs worked and what songs didn't... keeping in mind that figuring out the right songs is only half the battle.. getting them in a good ORDER is a whole other issue.
The real key is that you're all creative folks and you're all trying to move your band forward creatively and cooperatively... that is a good place to start. Sure there will always be groups that orbit around one supreme talent/artist, but most of the best bands thrive thanks to their "us against the world" energy... and you don't want to lose that by bickering over which song goes were. You can really feel the difference - watching a tight/cooperative band vs. watching five people who just happen to be on stage and playing the same song at the same time. The audience can always feel that difference.
I think you got the right mindset - wanting to do what is best for the BAND and not for your songs (or someone else's) ... and anybody who feels like their songs are getting unfairly ignored well, that's what "solo projects" are for.