Those parts places are so happy to tell you that the parts have a lifetime warranty, but who cares in the grand scheme of things. If your 'lifetime' crappy ball joint goes out every other year it will cost you more time and money driving around to get a warranty part, doing the labor all over again, oh and don't forget that alignment you need to pay for AGAIN! And if you leave your bad part in the car for a long time, you could be paying for new tires or rotation because of abnormal tire wear.
Pay the extra for a superior part when it comes to suspension because it is a domino effect if/when it fails.....