Life jackets and PFDs have a limited service life. The amount of time they’re good for depends largely on the quality of the materials and manufacturing. It can go from a couple of years up to a decade, with proper maintenance and storage.
Storing your life jackets or PFDs while humid, in hot places, or exposed to the sun, could result in degradation. Low quality devices tend to degrade very quickly.
Always test your life jackets and PFDs prior to use. Squeeze them to half their thickness. It should return to normal very quickly. If it crumbles, it’s a goner.