Who has time today to cut controls as needed?  We certainly don't!  Reduced immunoreactivity in pre-cut slides may be an issue for some institutions, but I certainly do not see it here at our hospital.  Like everything else in the world of Histology/Immunohistochemistry it may be dependent on your fixation and tissue processing.  We usually cut 20-40 slides at a time and store them (not melted) in small plastic slide boxes at room temperature.  I frequently use slides that were cut over 10 years ago and do not see any problems.  However, each institution should perform their own QC to examine this issue.

R. Cartun