Using old slides for FISH

[Hans Dauwerse]

Does anybody have a method to regerated old slides to use 
them succesfully in FISH? 
The problem is that slides stored at RT or 4C dry out and 
will not hybridize anymore, than you have lost your precious 
material.
It sometimes work to do a pre-treadment with RNase and 
proteinase K (or pepsin) followed by a post fixation with 
formaldehyde. But this works only in a few cases.
Anybody?