With proper care and maintenance, a few hundred years.
A couple of hundred years.
A few hundred years or so.
Blue is a type of rust finish
Carbon steel guns are usually blued to protect from rust. Stainless guns are left as is.
Decades and decades
the browning BDA is currently valued at between 225-450 dollars for a gun with a blued finish and original finish ranging from 60%-95%.If the gun has a finish of nickel then the price range is 250-495 dollars.
Low for a "good" black polymer finish is about $260, to a high of $500 for a "NIB" high polish Blued gun.
A Matt or Matte finish is polished, but not to a mirror like degree. Somewhat like a satin finish on wood, it tends to be non-shiny. Of course, blued means the standard black finish used to help protect the metal from rust (it is a form of controlled rusting that produces black iron oxide)
100-200 USD or so
Impossible to answer without seeing the gun. The last 'excellent' gun we looked at had actually been horribly buffed and then salt-blued. sales@countrygunsmith.net
I believe the gun was manufactured in 1977. As to value, it depends upon finish and length of barrel. I have a blued 4" and think it is worth between $400 - $500.
They last forever. Or at least until you die and your body rots.