Battery charging

It's well understood that heat increases internal corrosion and reduces battery shelf life. And as you say they are getting more cycles annually in FL. So the GC batteries should last longer in MI.

Their effective capacity is reduced by cold though, because the chemical reactions slow down and the battery internal resistance goes up. So
their voltage will drop off faster and it will appear the the battery needs to be replaced. But that effect is reversible. Warm them up and you should get the lost capacity back.

So it is likely that you are replacing them prematurely, in order to have fresh batteries with enough effective capacity in cooler weather to get through the day. You might want to try keeping some and seeing how they do in the hotter months in summer, or take them to FL for the winter.

yes

OG I agree to an extent with you as my batteries stayed outside through the winter here in the Nor'east. I'm a believer that batteries are meant to be used, not stored so I disconnect the batteries during the winter and setup a low draw to keep them working (led light). This meant charging once a month.