But when life is good, it's hard to stop tinkering. Weekend-sized projects are the best. For me, it's an urge to create and see the core 20% come to life, not to maintain the boring parts over time.
Hormonal fluctuations is an interesting theory. I always thought it's just a need for variety -- sometimes consuming (i.e. developing taste, curating, exploring), sometimes creating, sometimes relaxing. For me the cycle is months at a time.