How do you guys store your decals?

In the original package in a cigar box in my shop on the lower shelf of my smaller work bench.

Given that I can leave CA bottles open until I run them dry, I don't really worry about keeping things dry,

Actually, if you keep them too dry, the film will crack and they can disintegrate when you put them in the water. Of course that is worst case, and they have to be pretty old to have that happen.

I don't have a lot of them. I just keep them in their package an put them in a hanging file in my filing cabinet. Dry transfers in another, and vinyl letters in a third.

I've organized my scraps/half-pages in a binder ... using clear plastic pockets ... similar to a postage stamp album.

I've "glue sticked" some to pieces of paper to help keep them visible in the pocket.

Many years ago when I was heavily into building plastic airplane models, I used a product that was basically liquid decal film applied over old decals.  When dry, you applied decals as usual.  Surely something similar is made today.

It saved a lot of old, irreplaceable decals.  

Microscale makes a product called Liquid Decal Film.  A good hobby shop should have it.  I've used it and highly recommend it.  They also make a couple of good decal setting solutions.  There may be other products out there too. 

I store my decals in their original envelopes in a file cabinet in my train room.  It's in the basement and remains rather cool.  In the Summer, I have a dehumidifier running and in the Winter, it's (partially) heated.  Rarely too hot or too cold.

I store mine in the original packaging and then in a plastic bag. Most of my decals are Microscale brand, and they always need to be over sprayed with glosscote to keep them from breaking apart when they are applied to a model. Even with glosscote a good decal setting solution will make them snuggle down into the nooks and crannies.

Jeff C