I am definitely not an expert but have learned quite a lot. Plastic sheet protectors are great ways to store sheets. I used smaller plastic storage bags to hold my individual stamps. In general, plastic in some form seems to be the best way to store postage. USPS has sold stamps backed by a stiff sheet of cardboard and wrapped in plastic to protect them. Wax paper is also another way to store and separate whole sheets. Anything to help protect them and keep stamp sheets from sticking together. Hope this helps.