[mort1merp0]

It really depends on which type of stainless steel that is used. Some, like 400 series, will in fact rust.

Others, like Hastalloy and Ferrallium, have very good resistance to corrosion. A company I worked for used these metals for burial containers that were certified for ~300 years.

[anfilt]

Again hundreds of years, still a heck of lot better than plain iron. Although there is concrete that is older than that some well over 1000 years.