I don't keep my supers in the fridge at all, they die... I don't feed my waxies either. The only things that I keep in the fridge that I actually feed is my mealworms. I take them out 1-2 times a week for the day, and feed them then. Then I put them back in the fridge.
For superworms, I personally keep them in a bran and rice infant cereal mix and add in collard greens, mustard green, dandelion greens, sweet potato, squash.. what ever i am using to gut load crickets with. They eat it up. Just be sure that if the dry bedding (bran/cereal) that they are in gets damp AT ALL that you change it to remove the risk of mold or bacteria buildup.