That's a good question that I think is better answered by folks with more experience than mine. I'm going to guess that ISOMs are aged more frequently than non-Cs and so a year is used to identify as well as the name. I don't think there are years that especially mark good quality - could be wrong though - but some years are better in regard to bumper crops. I know some ISOMs don't need any aging to be very good.

Along with your question, I'd like to know what cigars especially benefit from aging - ISOMs or otherwise. I'd think that if someone were to invest money in a high end box of cigars of any kind, they'd be prone to invest the time as well.