I think the safest bet is to check your archive media every couple of years no matter what format it is.
Else you'll end up with all your files either being inaccessable due to the quality of the media or the fact you have nothing to read it on. CDs have been around for quite some time and most likely will for the next couple years, but keeping the data in formats that might not be readable then could hurt. The fact that I have some thesis work stored in MacDraw on a CD-ROM does me no good if I have no software to read it.