Flash technology works in such a way that CompactFlash cards wil eventually "wear out". This happened to one of my cards at a wedding, and experience I did not enjoy (I was able to recover the data with PhotoRec).
I'd like to figure out the relative ages of the cards I've got (after I had the problem at the wedding, I standardised on using SanDisk cards). While clearly the relevant fact is the number of erase cycles each card has had, I did not record this, or the year of purchase. But if I can deduce the year of manufacture, this could be a reasonable start.