I like to work some off-season leagues but I've become very picky about what I'll do.
It has to be 3-person and my partners have to care. The quality of ball and my partners have to be quality enough that I don't develop bad habits. I will work with newbies if they truly want to improve.
I also get some off-season work by going to camps.
And being an evaluator at camp has helped me a lot. It is amazing what you can learn by teaching.