X2 on the good quality sewer hose, we use the Rhino hoses. We have been staying a month or more at sites (we are full timing this year) and have tried a couple of ways. I will always let the black get full then dump, you do not want to leave this valve open all the time or you will get solids building up in the tank! I have left my gray tank valves open, then about a day or so before I need to dump the black, I will shut the gray valves so that I have a tank full of gray water to rinse the hose after dumping the black. When doing this, leaving the gray tank valves open most of the time, it seemed that I was getting some soap scum buildup on the hose?? So this past month I have been leaving the gray tank valves closed and dumping them only when full. I will know in a couple of days when I break camp if this is working better. IMO, if you are going to be away from the site for a few days or more, I would close all valves. If one of your traps dry out, you could fill the camper with sewer gas!
TV, 2000 Dodge RAM 2500 Quad cab short bed, Cummins 5.9, Edge Comp, Gauges.
5ver, 2011 Palamino Sabre 31 RETS.