If you examine the product history of companies that have been in the business for a significant amount of time you will see numerous changes is design philosophy and many "dead end" product lines.
This is exactly what NOT to look for in a company - what are the chances that this years model happens to be a keeper? Successful products with substantial advantages often have a much longer life span - some lasting 20+ years. If you can find a product that is still being produced (substantially unchanged) and is desirable 5 to 10 years after its initial launch then go for it.
Today's latest and greatest mostly ends up on the "dead end" junk pile.