Just to follow up, I confirmed with Renogy tech support that the warranty on their bendys is 5 years on materials and workmanship. No output warranty at all.Renogy has very good prices and a solid warranty on their rigid panels but the warranty coverage on the flexis seems to be much thinner. I don't know whether it's the cells themselves or the polymer encapsulate but I suspect the latter. I'd like to see some test data on how the encapsulate degrades over time with UV exposure.
Of course, all the warranty in the world won't help you if the company goes bust. Not an issue with Kyocera, Siemens, etc. but it can be with the smaller outfits. If the upfront cost is cheap enough, it can be worth the risk but it's always worth keeping in mind that the risk is there.