40AH battery life

I got the 40AH battery and charger from JAVAD less than a year ago and I'm having a hard time getting 8-9 hours and the last hour is reduced range. I charge it every night and its fully charged when I start. It reads 7 watts output after 8 hours. I'm having to hook my truck up to it and ride the 4wheeler.

My question is is this the life expectancy of these batteries about a year? This past summer I would work it 12-14 hours no problem? Is it the cold weather? Thanks.