I do not understand why everyone pushes the 120 volt machines more than the 12 volt machines. I have two. One for 3 years, and one for four years. They easily run 40 hours a week, with the hot water on. I have had to replace two batteries, one for each machine, and that is about the same rate as I have to replace car batteries, and have lost the charging system on each machine, at three years. I have had a bigger problem with Vanguard motors than I have had with my 12 volt systems, and they still have a lot of life left in them.
Scott