I bought these for work as when the company ordered their own brand safety knives, the delivery somehow never came in, and I was tired of breaking my nails on boxes or having to use a screwdriver instead.
I do 12 hours a week and use the knife excessively during this time, and three knives have lasted me 6 months, with two still intact, but blunting, and one that broke on me when I dropped it this morning.
It surprised me that it broke when I dropped it, as they're usually pretty durable. I'm always dropping my knife and that's the only one to break so far.
The keyring, unfortunately, comes loose almost immediately, after you grip the knife about 8-10 times, especially since I'm putting it in and pulling it out of my pocket about 400 times in 3 hours. But for me, that doesn't matter because the keychain isn't necessary.
All in all, even the blunt knives still do me well, so, as long as you don't mind buying more every 6 months or so for sharpness, they should serve you well.
(That is, if you're using it for work. Solely using the knife to open parcels, etc., they should last you much, much longer).