These are questions that are best to contact the manufacturer directly to find the answers.
Many people (including myself) buys life jackets and they seem to use them for a long time, probably longer than the recommended lifetime of the product. If they are used sparingly and maintains in good shape, they may appear to last for decades, but often, it is difficult to determine if the integrity of the foam (that provides floatation) has degraded or not.
As for regular maintenance, washing and cleaning the outer layer is recommended but not with any harsh solvent, as harsh chemicals can damage the foam (or even the outer layer). Dish soap is adequate in most cases. Store the life jackets in cool and dry places. Heat and UV can weaken the foam, and mildew or molds can degrade the foam.
You should test bladder types at least once a season to be sure they actually inflate and hold air. Use up a cartridge (preferred as it is dry air) or use the mouthpiece. Never leave them in your car on a blistering hot day...... not good for the bladder and tubing.
Cheers,
OldTimer