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If you do not damage a brushless motor, it should out-last your aircraft. If you damage it, there's no telling how long it will last!

Damage chiefly comes in the form of:
1. Bent shafts. Running with a bent shaft will destroy your ball bearings.
2. Heat. Anything the motor does generates some heat. Anything which makes it work harder generates more heat. Running it at too high of a voltage, or too large a prop, will eventually damage the motor through too much heat. Poor ventilation can do this too, even for motors running in spec.
3. Too high of RPMs. This is rare, but you can throw magnets running the motor significantly faster than it's supposed to. Usually this only happens if the attached prop or rotor is badly out of balance; the combination of high RPMs and excessive vibration throw magnets.
4. Crashes. This can do all kinds of bad things to your motor.

Note that none of those is "time". A brushless upgrade, like you bought with the hop-up kit, doesn't have a service lifetime. Just a warranty. It will eventually wear out, sure, but a well-made one will run for years without.

I doubt you'll find any Blade owners with the brushless upgrade who have worn out their motors. It's crashes, mostly, that do that, and the service lifetime will be "some finite period after your most recent crash".