John, did your tapatalk work? I don't see a reply.
I entered a reply, then edited it, and then tried to delete it until I could check out some info. All I could do was erase the comment and leave it as a blank post. This is from my laptop at home.
At any rate, concerning my set up, the quick connect fittings do not interrupt flow when they are disconnected, they only make connecting/disconnecting much easier. The shut off valve in my filter box, between the regulator and filters allows me to disconnect the system there to pull the filters out of the box for servicing without dumping water all over. It's also another shut-off to the supply into the rig should any prankster turn the water back on while we're not there for an extended period (hasn't happened to me, but to others I've read). There is a valve on my manifold in the UDC that also shuts off the supply, so they'd have to bust in to mess with it.
It's been my experience that the carbon block second filter lasts the entire summer, based on water usage. As far as flushing it before use, I do that at home just before we take the rig up for the season. The sediment filter gets changed about mid-season if I see a pressure change indicating it's getting clogged. I have a gage before the filters and on the regulator, so I can see if there's an increased loss in pressure across the filters. And since they come in a pack of two when I order them, it's no big deal to just change it mid-season and be done with it.
Concerning the length of supply hose I have, it's a 50ft. one from RV Water Filter Store with stainless steel fittings. I bought it before the 2013 Goshen rally after finding I had to splice two hoses to reach the spigot at the same site we had in 2011. Since it's more than I need at our CG site, I coil the extra on a hose stand next to the pedestal and drape it over the tires under the kitchen slide and cover the stand with a white garbage bag. Keeps the droppings off and I don't have 50ft. of muddy hose to clean when leaving in September.
Sorry for the long post.