As said elsewhere, my bikes are categorized by purpose, so usually get a weekly rotation: Tuesday and Thursday are grocery runs, so Trek w/trailer. Yokota is any days when the load is light (rear rack and/or pannies) or non-grocery wet days. Armata is when it is dry, no rain coming, and/or I just wanna freakin' fun fast foray!
Helps that I can only afford to have and store 3 bikes