why does my toyota eat front wheel bearings?

[Donna m]

My mother has a 93 Toyota Carola DX that has been going through wheel bearings about every 2 months.After previously replaceing the wheel bearing more than once.The half shaft and assembly was completely replaced with a remanufactured one. Every thing seemed to be going along fine. took the car to les schwab for front end alignment. when we picked up the car, we had only made it about 3 miles when I finally asked "what is that noise any way"It sounded to me like some thing was about to sieze up or fall off. As my mother and I each assumed since we just picked up the car, that we were just amagining things.We went back to Les schwab.After one of the attendants test drove the car he questioned us as to what the noise was we heard.( i didn't see how it wouldn't be perfectly obvious) He told us he thought it was "probably" the wheel bearing.I couldn't believe that some one else wouldn't have known the wheel bearing was going bad since we had just picked the car up 15 minutes before but... So, we ordered bearings from NAPA again...installed them and about 2 months later same thing , Noise and inspection and replacement again. This time my dad sent every thing in to have the bearings machine pressed in. Thinking maybe that was the probllem.and less than 2 months the car sits again waiting for pay day to be fixed again.Any ideas? I'm sure there is some other problem that keeps causing this to go out but we are at a loss for ideas.