While side projects are good you are going to need more to stave off burn out, consider taking a painting class or learning an instrument. You need something external to the computer to expand your horizons, burn out is a combination of issues, but one of the big issues is that as a group developers like to learn and at a certain point we peek in a language their is just not that much to learn that is interesting, when this happens that need to learn has to be focused on other outlets.