Try to find out what kind of charger/converter you have on the rig... My MH has two of them (one added) The factory installed a Progressive Dynamics Intellacharger with Charge wizard (I truly like the spec sheet on that unit) and after market I had an inverter installed... Xantrex Prosine 2.0 {that's 2000 watts of very clean 120Volt AC})
The intella charger with charge wizard is designed to be left plugged in all the time with monthly monitoring of the battery levels, it automatically performs many of the maintance tasks such as equalization of wet cells (Note, Some batteries do not like this, mine do) and such. The Xantrex also is a 3 stage charger but I have to manually request equalization... Which is better for other types of batteries.
NOTE: it is best to keep batteries charged ESPICALLY if you live where it gets cold.
A fully charged battery is very hard to freeze,, A discharged one goes all to pieces at around 30 F, And that is not a good thing on many levels (By go all to pieces I mean the liquid, which is mostly water in a discharged battery, turns to mostly ice, expanding and breaking the housing, then when it warms up it all runs out, and of course damages anythign it flows over on it's way to wherever it ends up,, As I said, not a good thing)
Note 2: I am not familure with most of the charger/converters out there, I know the two I have, simply because 1: I have them and 2: My mother did some consulting work for Progressive Dynamics many moons ago. Do not take my post as a recomendation of either of the products I mention by name over another brand. Do your own investigation.. Progressive dynamacs (obvious url) gives you some good info