Good drawn combs are very valuable, which is why I find it surprising that so many beekeepers neglect them. They will rapidly deteriorate if they are neglected and will become useless.
Combs keep in best condition when occupied by bees on hives, but that isn’t always possible. When in store there are a few things to be aware of, including vermin such as mice and rats, wax moth and dampness.
There are a number of things advocated for treating stored combs with, but in my opinion common sense is the best option. If combs are stored wet they will be attractive to rats who will chew holes in boxes if they are not stacked properly. Mice will make a nest in boxes of stored combs if they are allowed to enter them. Combs aren’t usually any good afterwards.
Greater wax moth can quickly destroy combs that have had brood in, especially in warm weather and if the combs are stacked together. Lesser wax moth will attack combs whether they have had brood in or not, but are not as destructive as greater wax moth.
I place shallow combs in supers on wide spacing and brood frames on narrow spacing. They are dry and placed in a stack with a queen excluder top and bottom and a roof on top. They are left outside or under cover in the cool. In winter this will reduce the activities of wax moth. I make sure there are no gaps for mice to enter. I rotate my super combs, so what I don’t use one year are the first to be used the next. This deals with lesser wax moth.
I have never used any of the substances that are often advocated for treating combs with as I find the above is adequate. It’s simple and effective.