I know nothing of metalurgy so I speak only of the risks I'm willing to take based on the experience of many shooters in Europe and the US.

I have a 16 gauge Joseph Lang built in 1866 with replacement damascus barrels by James Woodward most likely from 1872 or earlier.

I have a 12 gauge J&W Tolley with the original damascus barrels that dates between 1887 and 1894.

The Woodward barrels on the Lang were reproofed at 900 BAR in 1990. The Tolley was reproofed at 850 BAR in 1989. The Birmingham Proof House obviously had no concern about the barrels because they passed both view and proof firing and they applied the marks indicating reproof.

I shoot both of these guns and have no concern that the barrels will fail - provided, of course, that I shoot appropriate low pressure loads.