As for what is causing the drain, there are several systems that always get power, for one the vehicle computer, the memories in the radio (And it's clock) and I'm not sure what else. Doing a full chassis battery disconnect may be impractical on modern computer controlled vehicles. The reason I say this is the computer on many vehicles "Learns" the vehicle, this can take up to 500 miles and as it learns it fine tunes your fuel/air, timing and selected other settings so as to get best performance. Disconnecting the battery for an extended period resets it to "Out of the box" so for the next period of miles you are re-learning and thus costing you added fuel.
However one factor in a deep discharge recovery... I've used several brands of batteries on my towed. Most of them, one deep discharge and they are toast. Whatever they put in the last time has survived several deep cycles. So brand of battery can help.
Second, Tell us a bit more about your coach
What brand of battery
What brand of converter (For the house) (and model)
What brand of battery control center (And model)
I keep my coach pulgged in 24x7 and the result is a fully charged battery all the time.
That said, the last couple of camping trips it was telling me the chassis battery was dead. So before heading for warranty replacement I decided to do a load test, crawled under with my load tester and ... It passed
And after re-connecting it... The rig started normally
Humm... Bad connection? These happen most often on the ground lead, and often as not at the CHASSIS end of the wire, However nothing prevents the other wire from having issues as well