I have several battery tenders for my vehicles that are connected all winter while I am in Arizona but those vehicles have sealed low maintenance batteries. And by the same token My RV with 2GC batteries are on a PD converter/charge wizard all winter and I have not needed to add any water during that time.
I think you would be fine but if you use a timer on a tender I think it would be better to charge a day or two a week so the battery tender can go through all the cycles while it is turned on. I think that would be perfectly safe.
The battery disconnect on my fifth wheel opens the positive cable that comes from the batteries so there can’t be any possible draw. Craig