Mine got changed from age, not miles.
Though the pulled ones looked fine.
the materials these gates industrial belts designed to run 24/7 at much higher loads than a camshaft with 90lb valve springs, that honda uses as timing belts don't easily age unless sitting in the desert sun for 20 yrs. If age was a concern Honda engineers would have provided an age change out interval. Also to note, the design of the original Gates belts used in 1988 and since been upgrades to what is avail today.
Construction consists of these components:
1. Fiberglass Tensile Member — Provides high strength, excel-
lent flex life and high resistance to elongation.
2. Neoprene ® Backing — Strong Neoprene bonded to the tensile
member for protection against grime, oil and moisture. It also
protects from frictional wear if idlers are used on the back of the
belt.
3. Neoprene Teeth — Shear-resistant Neoprene compound is
molded integrally with the Neoprene backing. They are precisely
formed and accurately spaced to assure smooth meshing with
the sprocket grooves.
4. Nylon Facing — Tough nylon fabric with a low coefficient of
friction covers the wearing surfaces of the belt. It protects the
tooth surfaces and provides a durable wearing surface for long
service.
https://www.gates.com/content/dam/documents-library/catalogs/powergrip-gt3-drive-design-manual-en.pdf
