20000km/1 year is the standard warranty with Bilstein's, for a product which has such a great rep and everyone says they are the best, the warranty is pretty average, especially as some aftermarket shocks come with 100000km/3yr warranty.
I bought my Bilstein's from a local joint called Fulcrum and in the final stages of my purchase he said he would warrant the Bilsteins for 3yr/60000kms, which is why I ended up going with them. I dont know if he is doing that off his own bat or it's a fulcrum thing, he may have just said it to make a sale, but Ill be holding him to it if I have problems