I don't know if proven but I would always leave fluid (water in summer and rv antifreeze in winter) in the system to keep seals, pump membrane e.t.c. lubricated.
A gal. or so in the black tank and a 1/2 - 1 cup of dish soap now will do the trick, no need to waste money on fancy chemicals and no need to wait.
2013 RAM 3500 Longhorn Dually, Andersen Ultimate 5th Wheel Hitch,2014 Trilogy 3650 RL, 8000# axles, disk brakes, I.S., 960 Watt Solar