What small generator issues show up every December?

[HoennBirch]

I am doing some pre Christmas generator checks and it feels like the same small issues always start showing up once the weather turns cold. Nothing major yet, just the kind of things that get ignored until December forces them into the open.

What do you usually find this time of year. Low batteries, sticky transfer switches, fuel issues, loose connections. I am curious what patterns others see so I can stay ahead of the usual holiday season surprises.