I purchased a pair of Inov8 Roclite 345 GTX boots (from an internet site) and within 3 months, I had walked 1200 miles in them on my Lands End to John O'Groats via the 3 peaks walk. On my blog I criticised the Gore-Tex (waterproof) linings for leaking after 300 miles again. I was surprised to receive a message from Gore-Tex asking me to contact them. They collected the totally worn out boots and took them back to their repair and testing centre in Germany. After a week or so they sent me a full good will refund for the full price of the boots.
I stand by my criticism of the linings as I have had 3 pairs of boots fail around the same mileage, but I am extremely impressed by Gore-Tex customer service.
I recommend you read Gore-Tex guarantee if buying a pair of boots with a Gore-Tex lining. It is worth the paper its written on, as they say.
If interested, there are more details on my website: wildwalkinguk.com