The owner's manual for my 2005 GTO with a computer says to disconnect the negative cable if the car will not be used for a few months. I'm pretty sure that's what is done with cars fresh off the assembly line that are unsold and parked outside in an inventory lot. A good disconnected battery will hold its charge for quite a while, just as the disconnected batteries for sale on retail shelves mostly stay fully charged.

Next spring simply put a charger on your disconnected battery to top it off. The meter on your charger should show (1) the battery doesn't need much charge, that is, the needle isn't far from zero, and (2) the needle should go to zero and stop charging in a short while, say an hour, indicating all is good with the battery.

My wife's 2018 car was manufactured in May 2018, and she bought it in October 2018. So the battery was probably disconnected for nearly 5 months. Not a problem.

I have a battery tender, but don't use it here in Texas. I don't see any need for them, even up north. As said, next spring, simply top off your battery, and you should be good.