I came across this during a search of filters: Filter Barn - Caution and Recommendation - iRV2 Forums (http://www.irv2.com/forums/f258/filter-barn-caution-and-recommendation-192952.html)
Sometimes there is a good reason for what seems like a great price.
After all these years I never thought about filter shelf life, or even thought to look. Learn something every day, just running out of storage space ^.^d