use them hard on a rainy day, and put the bike in a garage for a week. Tell us if they rust.
Stainless ain't always stainless, there are many grades, some work great for rotors, some don't. Some rust, and some don't....
oh, if they warp, $220 was a costly gamble. Not to say EBC would give you new ones if they warp, but I'd think you would have a better chance of it.