"Shelf" life of polishes, sealants, compounds, IE, liquid products will vary depending on the particular solvent used and what emulsifier.
Most of these products will have a normal "shelf" life of two (2) years if kept at a normal room temperature of 85F down to 45F.
One "high temp" exposure will often cause the emulsifier to start to break down, one or two freeze "cycles" will do the same.
With the advent of newer Federal and some States changes to the VOC content of products, many manufacturers of such products found it necessary to change the "solvents" used to meet the new regulations.
This change often required the use of a different emulsifer, however, many of the formulating chemist were not aware and stayed with the older emulsifer when moving to the VOC compliant solvent systems.
That said, some products did not require changes in the formulation and are able to retain stability for over 4 years.
Even the selected container for packaging may affect the shelf life of a product, say the manufacturer moved to a less expensive bottle/container, however the florination level of the plastics was at a lower level. This allows the solvent carriers to migrate out through the sides of the bottle or in rare cases, air to infiltrate into the container.
Since most of today's polishes, liquid waxes, sealants, etc contain one or more polyaminosiloxane resins, this creates the concern most experience due to these resins being "aerobic" curing-(IE-air is the curing agent for the resins, so when exposed to air, they start to "cure or catalize")
Hope this helps all to an understanding of why things are not as they were 6-to-10 years ago.
Grumpy
