You raise a good point, which makes this even harder to do right. What is the "life" of a particular product? Sure I could buy a pair of hiking boots that would last me for my literal lifetime, except that I'm already 50, and I "hike" a short public trail about once a year.

My dad, however, always carries a pocket knife (for fishing purposes), and I've seen them get so much wear, the inside of the blade starts getting worn away from being sharpened so often. What's a "lifetime" for someone who sharpens a knife every other week? That's going to wear out even a "BIFL" pocket knife much sooner than "life" would lead you to believe.

There needs to be a way to incorporate the duty cycle of the thing being reviewed, and length of time owned, but then you're just back to the problem of people gaming a review system, and the commercial internet has ruined everything.