Hub Assembly and Wheel Bearing

What is your question?

I have a 2006 Mazda 6, and The left hub assembly is going bad for the fourth time. First time i just changed wheel bearing, second and third time I've changed hub assembly and wheel bearing. Second time it was good for about 5-6 months, now it's only a month and already making noises. The car doesn't vibration at high speed, I don't understand the reason for the breakdown. The noise first sound like the whole bearing is sliding (thin jamming) later sound like tire noise coming from the front end - most noticeable in the 40-50 MPH range My question is this - what could cause a new (Japan Parts) Hub Assembly & bearing to go out so quickly? Your thoughts?