@Perspective; a little knowledge is a dangerous thing.
Large RPT aircraft components are NOT in the majority monitored "on Condition".
"On condition" means components like a light bulb in a toilet. If it fails, change it, there is no measurable effect on safety.
You probably meant: "Condition monitored" where it is possible to measure they safety state of the item, for example a brake pack, which has wear limits or an NGV via a borescope inspection.
If that is not possible we are back to hard time, hours or cycles or maybe by today real time time/temperature history logging.
Stuff expected to be rebuilt are "rotables" which have traceability (e.g. magneto, FCU, etc.)
All else is manufacturers repair scheme.
P.S. If the manufacturer says Four year time in service then that is the applicable limit as far as I'm concerned. Whats got me scratching my head is that I have a brand new engine and prop that are yet to be fitted or run. Should I overhaul them in four years from date of purchase? DAte of manufacture? Date of first run? If not the latter, then Australia will need "use by" dates and we will need to ask manufacturers for the freshest product.