Timing Belt Replacement

IMO, don't risk it... I wish I had concrete evidence for age being a factor as well as use, but I'll be honest I haven't seen any studies or evidence of it. I can say rubbers tend to rot with age, and generally speaking manufacturer's would prefer to tell you their vehicles require less maintenance than their competitors, so if they put that time line there, it's likely for a reason.

belts are given a kilometer rating way under what they can last for so even if its past the recomended kilometers your belt should still be good. as long as a belt is still tight and there is no visible damage such as cracks tears or wear from rubbing a belt should be able to last at least twice its rating. i know a guy with over 500 000 km on his old 84 dodge pickup and he is still running the factory belts with no problem

The oxidation rate of rubber is relatively high. I once purchased a five-year-old Mercedes with only 10,050 miles on it. Within a couple of months I had to replace the tires and brake pads. Shortly thereafter, I replaced all the belts as a precaution.