same thing happened to my pro lite 3 mat after 2plus years. Had no problem getting it replaced, despite having no receipts. Remember sleeping out near An Teallach and hearing the mat delaminating, couldn't for the life of me work out what it was, sounded like some strange bug. All was revealed in the morning.
delamination more likely on light mats as there is less foam to be bonded to,
thermarest will warranty this no problems
if staying somewhere undo the valve during the day,a rise in temperature causes air to expand, which blows up the mat, same with cold deflating mat, i blow mine up before bed so its not half full in the morning on winter trips
I've had lots of them go this way, just contact First Ascent. They're not strict about you having to provide receipts & doesn't matter how old the pad is.
http://www.firstascent.co.uk/contact_1.html
The delamination problem happens to me when I use a Thermarest for a seriously long period of time (every day for 6 months). I think the moisture in our breath can cause mildew in the foam although they might have started putting anti-bacterial stuff in the foam? Leaving a Thermarest in the heat with the valve closed can cause the same problem, not sure if that's covered by warranty.
Because of this problem I've started using insulated air core pads like Big Agnes.
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