I'm in Jersey, not as cold as NH, but can get pretty cold, 6 decent months of riding, maybe 7 overall.
My last few Yuasas have lasted at least six seasons, being charged in the winter.
Before a 1500 mile, five day sport tour last summer, I replaced the original battery in my '01 ZRX. It had 6 1/2 seasons on it and was working fine, I just figured trying to get a full seventh season out of it was not worth getting stuck on the trip.
Blue