I originally bought two pairs of Darn toughs in 2013. Both Light versions. Wore them like crazy-was living in Japan so didn't take much with me. Heat and wet in summer, freezing and slush in winter, humid all the time; I used the drier for all our washing as otherwise we'd never get it dry in our apartment! Awesome socks for me in all conditions. Eventually I wore out these first two pairs, but, they probably had at least 4 months of wear in them, each. All were worn through in my typical fashion in the forefoot. Most socks I wear out much faster than this in the forefoot, and I wear through my running shoe insoles really quick in the forefoot (I literally wear holes straight through the insoles long before the shoes are though their typical life expectancies). I've owned lots of other expensive high end socks in the past, these are easily as good as any of them, but, Darn Toughs are cheaper. Actually considering the relatively high amount of wool content (which is a big reason why they are so adaptable and comfortable in a wide range of conditions), I think they are the toughest socks I've had. Other high end wool socks I've had (I won't mention names, but, from the better companies) have worn out really quick compared to these.
I'd heard for years prior to getting my first pairs about their warranty, thought it too good to be true and probably only applicable to Americans. But a few weeks ago, now that I had two worn through pairs, I figured I'd ask them if they'd do a warranty. I really didn't mind if they said no, as I now own another six pairs, and would be happy to just buy more. I would have been happy to post them from Aus too (would have been 15AUD).
They responded and said they would happily warranty them, just send them some pics, and tell them what size, colour, models I want! I took the opportunity to get different colours so that I would more easily be able to pair up my socks. They arrived yesterday. No charge at all. Exactly the colours I specified (they didn't have to do that, they could have sent me the cheapest colours or whatever they just needed to clear stock of).
Darn tough are awesome. I can't recommend them highly enough. Superb company.