bill...
i am sure you will get all sorts of response to this question, so heres my two cents....trust me, thats all its worth....
whether they need it or not, i replace my batteries every two years...batteries usually fail catastrophicaly and at the worst possible time so it's just good insurance. i only have two also. i use an intersate deep cycle ($80) and a west marine 1000 "starting" battery ($90). have had great luck with both of those...
now all the guys with 26 6 volt and 14 optima blue /yellow/pink tops with billitt battery boxes (made from a "splashed" design) all run in series/parrallel with the 2000 watt honda generators can chime in....
gm