Hi Rob,
Just like with our 2350, your grey water tank is the smaller of the two. Some boondocking conditions allow the grey water to be dumped on-site in the adjacent brush. Check before doing so. If you can do that, along with adding clean water into your fresh water tank, you can easily double that 3-days to 6. If we can't camp-site dump our grey water along with adding fresh water, it's typically 3 days for us, ideal for an extended weekend get-away. That considers one shower each for my wife and I.
The 23 gallon grey water tank fills up quickly for obvious reasons. When ours is full, I open the grey valve and flood the pipes, then when the gurgling sound is gone, I open the black valve and flood the black tank with grey water. Doing so helps get our 3 days. Flooding the black tank with grey soapy water also helps to clean it out better when it's time to dump. That process came recommended by Phoenix during our walk-through when picking up our new PC at the factory back in 2007.
Remember, the mixing of grey water into the black tank "MUST" be done in the order I described. You do NOT want to open the black tank valve first to keep the nastiest stuff inside that tank. Bad black in the grey tank is a bad thing when the grey tank backs up into the shower pan. Get the idea?
Ron Dittmer
PS: I am glad you got your grey tank valve working properly again.