Shoe Shelf Life

I recently purchased a pair of Nike LunarGlide 6.  I like them and was considering getting a couple additional pairs but wondered what the shelf life is on some of these types of plastics/polymers.  I know I had a set of running shoes about 15 years ago I used them for a bit then stopped running for about 5 years when I got back into it I noticed little bits of rubber or plastic piling up at the end of the treadmill.  It appears that some part of the material used to make the shoe had broken down.  I'd love to get some more of these shoes but don't really want to make the same mistake again if certain materials in the shoe do indeed have a shelf life.  Since shoe styles are here today and gone tomorrow I hate having to research my "next shoe" when all I really want is just to buy the same thing I had that worked.  Thanks in advance for any advice you can offer.

I still have a pair of Lunarglide 2 as beaters and they have held up still. I left it out in the garage for months and there is no separation anywhere. Although I don't use them frequently the outsole on the 2s has great tread life same as the 3 and 4 surely 5 and 6. I would say shelf life about 5-7 years for the glue and little more for the materials. More wear will speed the process. Running shoes never go out of style and there are deals everytime. Just buy a pair when you need a new pair unless you like a certain style.