There will be some sort of degradation whatever 
you do, even if you put your cel in a cel bag 
inside a cel book, inside a drawer that you 
never open in a room where you never switch the 
light on ! That's life, nothing lasts forever.

So my opinion is that it's better to frame a 
very nice cel (being very careful off course: 
buy the best glass, expose it in a room where 
there's not too much light, not close to the 
bathroom, and so on), that way you can see it 
everyday. It's no use having a cel inside a 
drawer.