Bad luck with cheap parts
When you go to the auto parts store for replacement parts, the salesclerk will usually quote the price for “economy” grade parts. They're cheaper but not nearly the same quality as “professional grade” parts. Unless you're planning to junk the car in a year or so, you're better off spending more for the better parts.
I learned this lesson the hard way on my minivan with 200,000 miles on the clock. I bought “economy” tie rod ends. Big mistake. The suckers wore out in less than a year, forcing me to replace them again. This time around, I bought “professional grade” parts and paid for another alignment, making the economy parts a losing proposition. Thinking that experience was a fluke, I tried again with economy wheel bearings. Same result. Now I won't touch economy parts.
Learn from my mistakes. Whether you're doing the repair yourself or having a shop do it, if you expect the repair to last longer than a year, insist on professional-grade parts. They cost far less in the long run.