Again AGE is not the factor as much as condition.
New Damascus barrel guns, including "twist" and "stub twist" were available at least to 1909, when my Grandfather got his Ithaca, and I think were available from someone (with decreasing popularity) into the 1920s.
The age of a Damascus barrel does matter, but not the number of years. What matters is what the gun has been through, or could have been through in its life. A Damascus gun with an unknown history should ALWAYS be suspect.
Most know you risk blowing a Damascus barrel with a smokeless load, but many don't realize they can come apart with the blackpowder shells they were made for, as well, if the barrel welds have weakened.
My Grandfather had a stub twist gun. He was fond of it, and so was a neighbor, who after several years, talked him out of it. He bought his replacement in 1909, and since he was having the gun made to his order (chokes, bbl length, stock dimensions) he decided to go with the new "fluid steel" barrels. The stub twist gun unraveled several inches of the left barrel in the 1940s. (unknown if it was smokeless or BP ammo)
Its been a couple years since I last used my Grandfather's gun, but when I did, it performed flawlessly.
There will be NO steel fired through that gun in my lifetime, and my future heirs also know why. Its the best I can on that score.
I also will not put steel through my model 12. It was made in the 20s. Steel is the reason I bought an 870, in the mid 80s.
If you are in doubt about your Mossberg, why not ask Mossberg? They are still in business, last time I looked.