i would echo peterfiles comments about durability of alpkit mats – although they have revised the design recently …..
my alpkit mats – both mines and the mrs lasted only 2 weeks of continual camping on a 6 month bike tour ….. before blistering. They blamed us leaving them in a warm tent inflated how ever a quick link to our blog showed us to be moving from place to place every day leading to the failure – they did agree to replace/refund but it was obviously 6 months or so before i could send them the corners back !
we replaced them with kathmandu mats which picked up a few holes along the way and required repairing a few times but at least that was repairable – i tried various bodges with the alpkits including sewing the delaminated bubble through to the other side and then patching over but short of embroidering it into a patch it clearly wasnt working it would just pull the centre of the bubble in and make the delamination bigger !
for the cost of the alp kit + the kathmandu mats i wish id just bought a real thermarest with the advantage that had i had a problem with delamination i could have gone to one of the many thermarest dealers world wide and got it replaced !