Is 12v constant from hitch actually necessary?

I don't unhitch or unplug when stopping for one night if I can possibly avoid it. If we're stopped for two nights or more we're going to need the truck so everything gets disconnected anyway.

I doubt it would be possible to pull all three batteries (two in the fiver and one in the truck) down to any significant degree in one night, and it certainly isn't going to happen with our usage habits.