I've had a couple of sets of Q powerline pros for 6-7 years now , the kites wear out before the lines, just need to make sure you retie the knots every 12-18 months cos thats were they will break . I get a heap of kiting in all year round and my lines have had a heap of use , and they are still as good as new. I was ( and still am )looking to make up some new race lines and the mob in the US i got the last lot through said they dont deal them anymore the manufacturer of distributer was too hard work. I have emailed a few other surf shops and they were pretty much telling me the same thing.
I did find one mob who still sold it and was willing to sent to Australia.
www.awindofchange.com/