My suggestion would be 2 AGM batteries, but at a minimum would stay away from batteries marketed as marine starting or even marine dual purpose as those batteries are really only needed with very large engines. (Ref: Pbase-MarineHowTo)

One of the best IMO is Odyssey Battery which used to be available as Sears DieHard Platinum. Odyssey states a 3-10 year service life. As I am on year 13 on the battery I use most often, I'll be sure to eventually replace it with the same.