Have I been unlucky or is there something else that would cause failure?

Couple of months before Christmas I had a TRE go - properly knackered - so trotted off to Euro CP and got 2 more - put them on, got the tracking done - lovely.

Just been to get the tracking and balancing looked over - precautionary since putting the 18" wheels on, and guess what - Mechanic calls me in and says -both track rod ends have gone' and showed me the wheel wobble.
Can't really say I had noticed, other than a slight wander when I brake hard, but had mentally put that down to the lower profile tyres wandering a bit in ruts - anyway they are done - so will be getting replacements from ECP - just wondered what if anything other than crap parts / bad batch might make them fail..