| The logic of changing the timing belts every two years escapes me.
The only explanation that I can come up with is that without SOME time limit, the timing belts would drop off the owners maintenance radar scope. The usual reasons for maintenance on a time schedule, don’t seem to apply here.
For example, for oil changes when the manufacturer specifies a time criteria, they're telling you that if you ride every day, but for only short trips to work, your riding habits subject the oil to a more severe service so you should use time, not mileage, as a guide. If you ride 100 miles a week, but do it in ten trips, you should use time, not mileage as your criteria.
Motorcycle riding is often different. If you ride only for pleasure once a week for 100 miles, then you should use mileage, not time as your change criteria.
Timing belts are made of kevlar-reinforced rubber, much like some tires that have no such time limit on their replacement. It’s easy to understand a mileage limit on timing belts since (except under unusual usage) it correlates directly to cyclic fatigue and wear.
So what’s so special about timing belts that they need replacement on a time schedule?
If you buy a new bike and then put it your private collection and don’t ride it for two years do you have to replace the belts? Of course not. Conversely, if you have a track bike that lives at the red-line don’t wait to change your belts until 12,000 miles is up.
You need to use your common sense here.  | 
Shazaam!
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