I just received this from the NBAA:
FAA Clarifies Meaning of ‘Current’ for Mx Programs
FAR 91.409(f)(3) requires aircraft owners and operators to maintain their aircraft in accordance with a “current inspection program recommended by the manufacturer.” In a recent legal interpretation, an FAA attorney stated that owners and operators are not legally obligated to adhere to the most recent updates to maintenance instructions or inspection programs, and only the maintenance requirements in place when the aircraft was built apply.
According to the interpretation, “New requirements could impose financial and other burdens on owners and operators of older aircraft that they did not bargain for. It would mean that our regulations effectively authorize manufacturers to issue ‘substantive rules’…that is, it would enable them to impose legal requirements on the public.” Eli Cotti, NBAA director of technical operations, said that this interpretation allows operators a lot of flexibility, but added, “most operators subscribe to an ever-evolving program for the benefit of safety, reliability and maintainability.”
Maintaining an aircraft to the latest standards also maximizes the value of the aircraft and the insurability of the operator, he said.
Here is the Legal Interpretation