We shall see how long the Integrity/Ultrex ones Paul and I have used last!
When you renovate old windows, how much do you change? If you leave the wonderful sash weights, then there remain those big, open, uninsulated spaces. Modern glass, beyond double-pane, has coatings that do a remarkable job of keeping heat out in the summer and in in the winter. There's a cost to fixing up old things, not just windows, that can make the labor excessive, if admirable.