Stuart Noble wrote:


The amazing thing is that some of it survives very well, but rarely on
the bottom of the window where it is most needed.

correct and if you examine old windows there is almost always a fine
gap between the putty and the glass which allows the rain to get down
to the wood and rot it.
I have had to replace windows that were 30 years old and yet some old
pitch pine windows are still sound after two hundred years. So his
talk of window age is more down to the quality of the wood than the
work of the putty.