Overhaul is recommended at engine TBO, or 10 years, whichever occurs first.
This is based on extended periods of sitting and corrosion is the #1 cause of contamination.
Moisture may be introduced which can be the beginning of corrosion and could be costly in a short amount of time.
Fuel breaking down causes acids to form, which in turn causes corrosion.
Extended periods of sitting cause rubber parts to become brittle, gaskets to become dried out, and springs to become weak. Also, jets may become plugged.
