Good question, and I'm wondering what sort of music you play. Your thread suggests you play Bluegrass. Banjo, fiddle, mandolin, guitar, and bass is, as you probably know, the classic bluegrass quintet, but there are many duos, trios and quartets out there. I'm in two musical groups, and we greatly enjoy making music together. One is a sea music quartet, the other a group of 70 Scottish fiddlers! So, much of it depends on how much you enjoy working with each other, and what kind of sound you want. Many musicians perform with more than one group, so they can be able to express their musical ideas with group types and sizes that fit the varying ways they want to explore music. Sometimes two members of a band do some duo gigs on the side together, because they want to express their music in a way the band as a whole does not. So, if these alternate routes are not a problem with the others in the band you're in now, you might want to experiment with those ideas.

-chanteyranger