as blizzard mentioned, I think road conditions do play a big role in the longevity of the coils. We're "lucky" I guess in the US because KW has a facility in California, so no need to wait the extra time for international return shipment in case of a rebuild. Keep in mind that a coilover isn't designed to last forever, you should expect to rebuild at least once during the time you own them (if you keep them for a while).
Mine lasted less than 8k miles before the left rear blew out. Haven't had any issues with the other 3, and the rebuilt one has been performing perfectly for a month or two now.
Between myself and friends, I've ridden on or owned most major coilover brands. KW's, for the price, have tended to be the most reliable and best ride quality for a daily driver. Obviously if you wanted to get really spendy, you can drop up to $10,000 per corner on some custom Ohlins or Motons, etc. but these are designed for the track and will require frequent rebuilds too.
in my opinion, stay far away from the "knockoff" or no-name brands for a part like this. As Gborja said, some other solid brands in this realm are Cusco and Tein. Lots of other JDM tuner companies make their own coils too, but these are often rebranded Cusco's or teins. (i.e. zerosports, etc.)
All that being said, I still think the KW is the best option out there for these cars at the moment. (price, build quality, ride quality, etc..)