prserving rubber boots

I just store mine away from sunlight and extreme temps, in a well ventilated area, and don't worry. I don't wear muck boots because my foot is so wide and they are so expensive. I've found a neoprene type boot at Ace Hardware that fits like a dream, and cost about $50. Shoe Goo will patch any hole. I suppose you could loosely pack them with dry newspaper in the off season.

my short boots and hip boots are still going strong after several years.
they are stored in a dark cool closet.

I wipe my hip boots down with Armorall (sp). I have a pair that are 20+ years old and the rubber is still soft and supple. Store them in the basement where it's cool and there is little light.