Noelle, I don't store slides for more than a month at a time. Biggest
reason is because I don't fix them before freezing. I put them in slide
boxes and then put the boxes in Bitran bags which are air tight and liquid
tight. You can put the desiccant in the bag instead of near the slides. I
don't get any ice crystals from humidity on the slides. Depending on the
procedure I either just bring the slides to room temperature prior to
staining or fix them. I have used the "Bitran" bags to store my OCT blocks
at -70C for years now. I get very little if any freeze dry affect on the
OCT. (all depends on length of time) Cover the tissue with OCT put in bag
remove excess air, seal. I have sectioned the blocks after two years and
still get antibody staining. (fibronectin and smooth muscle actin staining
are very comparable to the original cut) It all depends on what you are
looking for. Controls are a must. Sometimes the block needs a little
trimming around the edges but the tissue does not look lyophilized. I have
never had any problems with routine staining, or muccosubstance staining. I
try do all enzyme studies with new blocks. My theory has always been
storing in block form  is preferable to storing in section form if at all
possible. Let me know if you need more details. anita