Windows last hundreds of years because glass lasts hundreds of years.
Modern windows don't last very long, because the seals leak, and the argon gas or whatever leaks out. The glass is still good, but the insulative quality is gone.
The parent poster didn't realize that if you don't have double pane windows, you have single pane windows, which have no gas to leak.
Even if it's mostly air it insulates quite a bit better than single pane windows. Of course worse than with the original gas filling, as the windows are optimized for maximum distance between the glass panes without having the inner gas start to "circulate" - which starts to happen at a smaller distance for air than for the noble gasses.
Yes, for sure. My house is 65 years old, and all the windows have leaked.
But my point was that windows, the glass part, lasts centuries, if not longer. Not the mere decades cited upstream.