Sorry Carpenter but I beg to differ, I would say that most single ply membranes will last 25 years +. I have never had one break down and I'm roofing now for over 25 years, as a matter of fact you can get a 20 year guarantee on most single ply's and you won't get that on many other materials, Ever wondered why so many industrial and large scale buildings use this type of roof or are they just that stupid to throw their money away for a 10 to 15 year roof, I will agree with you regarding workmanship and the old green mineral felt which is on everyones house, if it lasted 10 years it would be time to change it, It sure gave the flat roof a bad name