I like to burn the Ardex 8+9 first into the Kerdi Band before seaming. and then give it another couple coats after for good measure.
The SK-25 mesh rocks from Ardex because it's perforate. You don't trap air bubble so it goes down nice and uniform and nice and tight. Great at rolling corners, inside and outside corners. I use my 3" taping knife to install it.
Pretty cool stuff.
Strong as hell. We used it to install some Schluter Profile to a tub deck. Amazing how strong it is.
You can email Ardex and get the warranty info. It's a pretty good tag team system.
I wish my Schluter rep told me about these products three years ago - could have saved a whole lot of bitching. lol JW