While I don't have any statistics. As far as computers I come across for various IT services and repairs. Even with laptops over ten year's old. Keyboard issues are exceedingly rare. Unless someone spills something on them or inherently defective design (Apple Butterfly).
I'd say it's far more likely something else will fail before your keyboard. Such as the battery, HDD, power plug, power adapter, SSD, various ports, display ribbon and LCD panel. Those are much more common failures roughly in the listed order of likelihood.