Back to the topic at hand: chargers and or battery maintainers.
My own opinion is, for those that care, is I'm not a fan. Never had one, never used one...and my car has ALWAYS sat idle in winter. Regardless of storage or not, I have always gotten about 5 years life out of a battery, and true to form, my Pagoda is on its 4th battery as it passes the 20 year mark post-restoration. So, I'm not exactly certain what the maintainer would do. Always, in the first start in spring, there was always enough life left in the battery to start the car. All my battery changes were pre-emptive.
Because my car was stored in a remote location during the winters for many years, the thought of something plugged in so far away was a bit frightening. Not all battery maintainers are UL listed. The thought of a potential electrical fire so far from a habited home for the potential of longer battery life seemed a bit unnecessary.
If you use one, that's your choice and decision: but if you do, do yourself a favor; ensure you have an AFCI breaker on the circuit that serves your battery tender. That will provide an enormous amount of peace of mind and in the unlikely event of any electrical malady (which may not be the battery tender, but the outlet or circuit itself) power will be shut off.
Here's a great example from our friends up north in Canada. It shows a "problem" electrical box, that is serving two devices within the current limit of the wiring (so the breaker does not trip); with no grounding issues (so no tripping of a GFCI outlet typically found in a garage). However, there's no AFCI breaker and THAT would have tripped instantly. Anyway, good to watch.
https://youtu.be/nPhgQpRFe5A While the example above is with a faulty connection, the same condition could exist with a faulty DEVICE attached to an outlet. You know, like a battery tender.