I know the older rubbers/vinyls, used to break down, become stiff and crack. What are the advantages/disadvantages to these current materials for long term storage?

Traditional natural rubber gloves usually have a stated shelf life of 3 years, and nitrile gloves are often rated at a 5 year shelf life for industrial applications. The things I've read about it said that the 5 years was a conservative estimate. The FDA hasn't established a standard for the gloves yet.

In regards to leaving them in the heat....I leave the Nitrile gloves in the bus here in Southwest Florida and have left them there for up to a month and I've not had them fuse together like the latex ones. Have some in my car to and not had them fuse either.

If you keep them out of the heat, AND LIGHT, I've successfully stored even latex gloves for ten years. We're talking 70 degree F longterm warehousing.

In a kit, I'd rotate them every year.

I buy mine by the box at industral safety stores -- a great resource for bulk stuff to put in kits.

TRO

The important part is to store them in an airtight container. I vacuum pack them in the food storage bags that came with my vacuum packer for food. The reason that plastics, vinyl & rubber, etc. become hard & crack is the loss of the lower molecular weight compounds in the mixture. Plastics are formulated to the desired flexability by combining higher molecular wt. ingredients with lower mol. wt ones. When the lower mol. wt. compounds evaporate, the stiffer high mol. wt. materials are left. Thus, you have less flexibility & more brittleness. Heat accelerates this process. Sealing the gloves in an airtight container retards it. This won't preserve your gloves indefinatly. Compounds with complex molecular formulas can decompose into simpler compounds regardless of storage conditions. Inorganic compounds such as water or salt are too simple to decompose. For more info, lookup plasticizers in the Wikipedia.