Just a few years ago (about 5) a study was performed in los vegas I believe, where the weather is dry and hot. they adhered TPO membranes from several different man. and found that they weather very badly in short amount of time. only like one man. came out with a decent report. within like 7-10 years. I cant remember who it was done by (one of the roofing organizations). If things change since then, then you are probably safe but for me it is still too early to take a chance with that type of membrane cause repairs are not very cheap and easy. I still see today a lot of seams curling up and even though their are tapes and such, even those fail as well.