I have a projector lamp that has been used over its life hours. Its still working though, no colour distortion, etc. But if I keep on using it, will it just won't light up when it finally stopped working or will it explode and destroy the projector?
There is nothing explosive inside a projector bulb, so "explosion" is the wrong word here. The glass envelope, however, can burst and that can shower glass fragments around inside the enclosure. I've seen this happen but I have never seen a projector destroyed by it.
An older bulb can be more likely to burst due to the extreme thermal cycling they go through so you should be looking at getting a replacement soon since this on has reached the end of its useful life.
The more clear danger with such a bulb is that the filament is close to breaking and that will leave you without your projector usually when you need it the most.
If used in a projector, any breakage would normally be contained by the projector housing.
Having the envelope (glass/quartz containment of the filament and halogen) burst is more common from poor handling practices (getting fingerprints on the envelope when installing the bulb) than from end of life.
Normally end of life is a boring filament break and nothing bursts.
"Life hour rating" is partly about trying to make sure that the projector does not go out in the middle of use in a professional setting (where you might be wasting hundreds of peoples time) and partly about driving profits (the company that cares about wasting hundreds of peoples time may have a different view of a bulb costing half what the projector does than a home user, but you can bet the profit on the bulb assembly is large in either case.)
Edit to add: LED "bulb" life hour rating is about maintaining rated brightness (and that is also a factor in halogen bulb life hours.)