It appears there is no Federal law, but many states require manufacturers
to at least provide some "satisfactory" solution to service problems for a
period of time after a product is discontinued.

That is so vague that it is unenforceable, unless you are talking about
products that are covered under warranty or extended service contracts.

This is what I was told by my friend at Sony, who heads the parts department.

According to her, the period of time is 7 years in California.

Virtually all products are implicitly covered by the common-law implied warranty
of merchantability. Enforcing it is difficult, and it appears that many state
laws have chipped away at it over the years.