One thing you can do that's useful is making sure you can still compile and run the code. The occasional minor off-critical-path edit could also be enough to give you that hit you need as a developer.
I used to make a point of submitting a minor contribution to every project's code. I used to (part jokingly) liken it to Alfred Hitchock making a cameo in most of his own films. The stated reason was to make sure I had the dev tools and env set up so if there was ever an emergency I'd be all ready to help out, and the unspoken reason was to help gain the confidence of the team. I think it was a good idea, but unfortunately the approach doesn't scale to work across large numbers of projects.