Do you get to practice regularly? Sometimes even just picking up the banjo (or a guitar, or mandolin, or whatever is handy) for even 5 minutes can help. A few stolen minutes can help both mentally and physically.
This may run against more official advice, but I always have an uncased instrument or two (or 5) on a stand where I can just pick it up and play it if the mood strikes me. Whether or not it is safe or practical for you to leave an instrument out is up to you. Sometimes, if it's in the case I won't bother, but if it's out, I'll play.