I'd remove them to be safe. I had left mine in over the winter last year (read that story here
) and I've been having issues ever since. Quite often the battery doesn't have enough juice to run the tongue jack, or the slide, or the lights are dim or something. Every time I think it's the battery giving it in for good, but then miraculously they come back as soon as I go to diagnosis it.
So far, nothing seems to officially be wrong, diagnosis always comes back that the battery's good, but then it'll fail me yet again. I've either shortened it's life by leaving it outside, or it's haunted.
So, yah, I'll be bringing my batteries in from now on.
As far as the fridge, I'd suspect it'll be fine in the cold. As long as it's turned off, drained of any condensation and the door's propped open to avoid mildew.