I haven't run them completely flat yet, sorry for the British term but it was the best I could think of. I have the monitor set to fire up the generator when the batteries get to 12v, but as far as I know it's never turned on to charge them. In other words, I don't know, but then I haven't been in a situation where they have gone dead. I had it set to 11v previously, but someone (either Thor or the dealership) recommended bringing it up to 12. I may turn it down some until I can determine where the safe spot is, and at that time I'd have a good idea of how long they will safely keep the house powered.
I did go out to dead chassis batteries a couple of weeks ago, and used the emergency start to start the truck off the house batteries. It worked. :)
