Might be worth asking this in the engineering forum... I'm not sure of an answer, but the bit of Part M that I think may apply is this:
M.A.503 Service life limited components
Installed service life limited components shall not exceed the approved service life limit as specified in the approved maintenance programme and airworthiness directives.
You can read that two ways - either it gets overhauled when the manufacturer says so or else if 'on condition' extensions are part of the approved maintenance programme, you could continue with present methods, meaning there's nothing to worry about...
Maybe someone more qualified in this area can comment?