I play in three bands right now, and am working on getting a 4th off the ground. I might also work with a singer/songwriter in her project, she sings in one of the bands I play with. Only one is predominantly original music, and that is the only band for which I could not conceivably get a sub. I agree with Jaywa's idea that one band should be the predominant band, and you let everyone know. But I also pretty much book "first come, first served" unless it is an unusual gig, a particularly good opportunity for exposure, to play a great stage, or collect an extra large paycheck. Communication is key- it's the only way it works. Being organized and managing your practice time is also very important.
All the pros in my area play in more than one band. It's the only way to make ends meet. Most of the semi-pros, like me, also play in more than one project. There would be too many lean months, and frankly, too many missed opportunities to play with different talented musicians to do otherwise. If I was in a band that was playing 15 - 20 times a month I probably couldn't play in multiple projects, but I can't see how one band could play that much without extensive travel. You'd just saturate our local market playing even 4 times a month. Since I have a day job, extensive travel is out of the picture. Thus I play with multiple bands.
About subs: if it's a cover band, how can you not find a sub? I don't understand Blue's situation, finding a guitarist to cover a blues gig should be pretty damned easy, frankly, unless you just haven't networked enough in your scene to know the right people. Playing in multiple projects and going out to see everyone else play is networking and puts you in touch with all the players in your scene.
The only jealousy problems I have ever encountered did center around booking gigs. When someone else books one of their other projects into a sweet gig, I can feel a bit hurt or jealous, wondering why they didn't book "us". I just make myself snap out of it and try to be a grownup about it. It works just fine. I concentrate on what I am doing, book one of my other projects, go hear other music that night, I just keep on trucking. Since everyone is in more or less the same boat, the level of maturity wins out and it's very liberating and enjoyable.
In fact, the only real problem comes up if one of the guys only has that one project- they then don't have the perspective or opportunity to not feel hurt and rejected and down the sh!t hole we all go having to go, hand-hold and ego-stroke that person. Dealing with passive-aggressive fallout for weeks or months afterwards. What BS.
For OP's particular situation though I would think about keeping 2013 for just your main band. It sounds like you guys have some momentum, you're putting out a new recording, you have a decent draw, and it's just this last year to make or break- I might actually throw myself 100% into that project, book furiously, push the recording on facebook and youtube, really immerse yourself there. Then if it goes, that's great. If it doesn't, all the rest of those other bands will still be out there waiting for you in 2014. I almost feel like you're in a special position in your musical career, I might try to maximize it just for the time being.
