Our 5th wheel is equipped with the Progressive Dynamics PD9280 Intellipower converter. It stays plugged in 24/7 except when in transit with the batteries on line. I have the Flow-Rite battery watering system, so battery maintenance is a 5 minute affair every couple of months. Typically, when I add water to the batteries, they won't take more than an ounce or two - I still have most of the gallon jug of distilled water that I put in the 5th wheel when we bought it almost 2 years ago.
On the other hand, I've had 5th wheels with "dumb" converters that would boil the battery electrolyte level below the tops of the plates in as little as 1-2 months.
So, it depends....
Rusty