I actually found a great cel book online that 
stands upright while still keeping cels nice and 
flat inside. It also has a slipcase to keep the 
dust out. Cost way more than a portfolio, but in 
the long run it may be worth it. I plan on 
keeping most of these for many years to come. 
Thanks again for the advice. And about my closet, 
I live in a desert so it is pretty dry all the 
time much to my dismay :)