My method is that as soon as I return from a trip with the RV, I FILL the FW tank with chlorinated water from a potable source and the chlorinated water stays in the system until the next time I use it. IF that next trip is more than a month or so since the last one, I first drain and re=fill the water system with fresh water. Empty but damp water lines and tank are a really good place to grow bacteria and having chlorinated water in there prevents bacteria growth. My whole house filter stays installed at all times except if I winterize the RV.
Good luck / Skip