Keep in mind, some vehicles are tougher on tires than others. Especially considering I drive it kinda hard, I'm lucky to see more than half the warranty mileage. With some alignment tweaks, I've gotten it to at least wear the tires evenly, although they still wear fairly quickly.
The closest I've come to hitting warranty mileage was with my old Firestone Destination A/Ts, which made it to 34k before I replaced them (1 pair just above the wear bars, the other pair had about 1 - 2 32nds more than that. If I'd been better about rotating them, I could have gotten about 40 - 42k before hitting the wear bars (50k warranty).
The Toyo Open Country A/Ts I have now are about 1/2 worn with a bit under 14k on them (50k warranty). I'm figuring they'll be worn enough to be up for replacement by 25k at the most. My General Grabber UHPs only have about 3600 miles on them, so they're still too new to tell how they'll last (hoping for 25 - 30k, but there's no treadlife warranty on them).
My mom's 99 Grand Cherokee has always been the same way with tires. They wear quickly (especially the fronts) and the fronts wear to the outside with stock alignment.