What bluewine doesn't seem to be able to comprehend is that, for some of us, being in an original band isn't about work, money, the amount of gigs you get or anything like that. It's creating something purely for the sake of creating it because you feel it needs to be created, not for what you can get out of it. I don't care if someone's gigging twice a week or twice a year.
As for whether the type of band you want to play with changes with age, I'm 41, I work full-time, am married and a dad (soon to be a dad again), and I have absolutely no desire to play covers. Nor do I have any desire to be signed (again) or be a so-called rock star. I want to spend my dwindling spare time creating new music with my friends. We're not expecting success, glittering prizes or mass adulation - for us, this is something we love to do, and it's nice if somebody wants to listen, and even nicer if they happen to like it.
My personal philosophy with music is that I never wanted to play the songs from my favourite bands. I wanted to be in my favourite band. Since most of the bands I love haven't been hiring for a bass player, that meant being in a band who could make music that I liked as much or more than the bands who were my influences. A lofty goal for sure, but, in two of the bands I played with, we succeeded.
It's nice if you can get some commercial success or lots of gigs, but it's not necessary for someone who makes original music to be justified in doing so - its a drive, an itch that has to be scratched. You need the talent to contribute, the right attitude and good people around you who share the same goals and communicate well. Yes, writing good original music is hard. So is playing the bass. The more you do it and the more you work at it, the better you get and the more rewarding it gets. And when you do get decent enough at it and get some gigs, there is no feeling like hearing an audience sing along with something you wrote. Having people dance to a groove you created. To see people you don't know on Youtube covering your songs.
Once you've had that, having an audience sing along with someone else's songs just doesn't really compare.
Hence the reason I won't ever play in a covers band. YMMV.