I think I was one of the first to fit them, over 12 months ago - done 15k, 2 ring trips and 5 track days. I have the car checked after each event and they're still 100%.
They've been making these for Subarus for years, so it isn't exactly new technology.
I'd say:
Dodgy batch.. or most likely incorrect fitting, failure to align suspension properly after fitting or as TT said and IMO too, dry joints.