I'm very lucky. I only play with one other guy. He's a better singer and guitarist than I am. He is kind to my shortcomings on guitar and vocals, and he digs the songs I write. We write songs solo and bring them to our weekly sessions in my home studio where we have time to play about 12 songs. We have over 100 original songs. We don't practice, we just play. Which means the lead guitar parts begin life totally improvised (and we are amateurs), and over time the lead player starts to remember the licks that worked and is able to repeat some of them. Songwriting is our favorite part, and we like playing all the songs. So that means we never get very good at any of them. I'd love to dial in a dozen songs, and I think we'd get good enough to play to a generous audience. But he has no time to play gigs, so that's not going to happen. I'm grateful that he likes playing with me and playing my songs, and I don't have to worry about an audience. I get to be both the player and the audience for three hours each week.
Sounds a lot like me with my other projects. (See post 29.) Lots of originals, lots of learning by doing. In the Americana duo, we're both big song writers. He's the stronger singer, and I'm the stronger player (flattop, mando, square- and round-neck reso, and blues harp). But I sing well enough and he plays well enough that it works.
We've been about a quarter originals, but we're about to shift to maybe two-thirds originals. We don't have a hundred yet, but we have a nice crop.
The blues project is fewer originals, but with the blues, you rewrite every song to fit your style, anyway, so every tune is half-original. I pick guitar, mainly, and do most of the singing, and my friend sings and plays blues harp. And we often drag in friends to play with us. We're not Sonny and Brownie, but we make it work.
You said it best: "We don't practice, we just play."