Some say yes some say no. I've never used one so I can't really say. I think were they may help is if the cart sits for extended periods without being used. I try to charge my golf cart batteries once a month during the winter and keep them full of water. The batteries in my red EZGO are 8 years old and still going strong.
I have one on my 90, unhooked for now. They run off the batt. pack so you have to charge it more often. After a month sitting, your pack is pretty much dead. A good test would be to drive it almost everyday and charge it often and see how many years you could get out of new batteries. Don't know if anyone has ever done this.