Water pump again?

My xj started making the lovely steel on steel death rattle of the water pump a few weeks ago. I pulled the belt and the water pump bearings are shot. My issue is that i just replaced the water pump last may. What happened? Did I tighten the belt to much and overstress the bearings, or did I just get a bad pump the first time? It's not that i mind the cost, because the one I'm replacing is still under warranty, the water pump is just a PIA to replace. What should I do differetnly this time to make sure i don't replace it again next year?

Over tightening the belt can do it. Maybe a flaw in the replacement pump. I tend to use quality antifreeze, the cheap stuff may lack the necessary lubricants.
Back in the day, water pump lube came as a separate additive and actually seemed to have some affect on pump longevity.
I also tend to look at what comes out when I drain the cooling system. It's not unheard of to get somewhere between a spoonful and handful of casting medium out of the water jackets. Had one motor that seemed to eat water pumps, noticed some sand (casting medium) in the bucket after draining the coolant. On a hunch I beat on the side of the block with a hammer, then flushed and ended up with most of a cup of casting medium in the bucket. I flushed and beat a few more times just to make sure.
I also drain at the bottom radiator hose, the coolant rushes out and seems to carry much of the junk with it.