We fix the sections before storage at -80C.  You can take one of the little
black plastic slide boxes (have lovely tight seals) add a small bag of
silica gel (blue, doesn't create powdery crud) and store your fixed slides
in a dessicated environment.  I tape around joints where lid meets body of
box, can be used as a label, then bring it to RT for 20 min or so, to prevent
condensation on instant opening of box.  Once the sections are thawed you 
should use them and not refreeze to protect antigenic epitopes from potential
damage. This works well for large staining run of 20 slides. 

I have also used slide mailers with lids, 5 slides per mailer, 
put into a one zip baggie, with silica gel, into a freezer, can remove a 
container of slides when needed.  Some people wrap the mailer in
foil, works well. Label with date, this is great for precut positive and 
negative control slides.   

Good luck
Gayle Callis