Tiny projects keep it new, for sure. It seems to tie in a little bit with proof-driven development and personal projects - in each case, you’re escaping the mental cage of a monolithic, mature product to start something new. (Even if the “something new” is a component that’s going to plug in to said mature product.)
Recently I’ve been dividing up the the Heroku architecture more finely. We’ve gone from about three repositories to over a dozen. Each time we carve off a new piece, it’s a chance to freshen things up. A new revision control system, a new framework, or even just a new class hierarchy. Breaking free of the past is liberating.