My Grandfather had an Ithaca 12ga double with "stub twist" barrels. Stub twist was a "poor man's" Damascus, being made from either 2 or 4 straps hammer welded, rather than the 6 or 8 straps used in "proper" Damascus. After many years of owning the gun, he finally gave in to a neighbor's requests, and sold him the gun.
Grandpa then ordered a new Ithaca, and got one with "fluid steel" barrels. This was in 1909. Sometime in the early 1940s, the neighbors gun had the left barrel unravel. The fluid steel barrel gun I still have, and its perfectly fine with light field loads, which is what a letter from Ithaca recommended in 1949.
Damascus barrels should NEVER be shot with smokeless powder, and its better if they are not shot at all, even with black powder, because there is simply no way to determine the quality and strengths of the barrel welds today. As was mentioned, rust can form in the tiny gaps inside the welds (and not be visible to even a detailed examination), affecting the strength of the barrel.
Even though it may have lasted over a century of use, and even if proofed with nitro powder, you should expect a Damascus barrel to fail at some point, and hang them on the wall.