I know don, DAMON gave me one when I bought this Intruder.. In the first year, plugged in most all the time I had to add water to my Interstate U-2200's ONE time (Mother's day, bought the coach in May of it's model year, or should I say took delivery in may) and in the 2nd year likewise, long about 4 or 5 years I had to water them more often.
During those first few years there were far too many times the voltage went below 12.. I try to avoid that now.
Still the U-2200's... Got replaced earlier THIS year (9 years after delivery)