Riding with a Gates belt past its due replacement mileage: can it snap or other risks? I just purchased a belt drive bike (Gates CD).

Maintenance free, according to the BS and what I have read online. The only attention is to replace it every 5000 km.

Since I usually ride around 8000 km/year, I was thinking to replace it once a year.

However I don't know what can happen by using a belt past its replacement swap mileage.

Can it snap like a belt in a internal combustion engine? Or, more in general, what are the risks?
The mode of failure I have seen in similar belts used in industrial applications are typically one of two types. In the first scenario the belts show physical damage. The teeth may start to separate or be missing. You may also see cracks on either side of the belt. In the second scenario the belt just snaps. A visual exam will show no wear, cracks or damage. What you will see is the ends of the internal cordage be it Kevlar, Aramid or similar fibers. The second scenario is common enough that belt manufactures generally suggest time or mileage intervals rather than visual inspections. Depending on your model (some are easier to change than others) you could carry a spare belt. As others have commented the belt breaking has some consequences other than inconvenience. Any unexpected component failure can result in loss of control and potential injury.