I used to be a "take it inside and store on trickle guy". But with two grp 31's in my boat, my back could no longer deal with them. For the last 10 yrs they have stayed out, disconnected all winter. Never less than 90% come spring. Ditto with my RV batteries - in fact, due to health issues, could not use it at all this year. Went to retrieve what I though would be a dead battery, and even after 12 mos, over a usual Minn. winter AND a pretty hot summer...battery was still at 80%.
Here's a link, scroll down to the chart for lead-acid time vs temp:
https://batteryuniversity.com/learn/article/elevating_self_discharge
If you live in a colder climate, just top off, fully charge, disconnect and forget until spring.
Fully charged, a battery does not freeze until below -74F, which none of us will ever see.....
