I got my first riding mower in 2017 and left the battery in the mower fully connected all winter (northwest indiana - we happened to have a fairly cold winter including -20F air temps for a couple days) to find the battery completely ruined in the spring of 2018. SO i bought the new battery and a trickle charger/battery tender that year and every fall since I bring battery into a mostly climate controlled basement (at least 65F all winter) and the same exact battery has started my mower without issue to the present day. That is 8 years by my math.
