In my consistent advocacy, I've emphasized the enduring value of restoring sash windows instead of opting for replacements. The inherent quality of the original wood, often sourced from slow-growth trees with heartwood, is a challenge for replacements, unless employing costly hardwoods.
The cycle of window replacements tends to kick in when new windows deteriorate rapidly. Therefore, salvaging your existing windows is not only feasible but almost always advisable.
For repairs, I highly recommend using reclaimed lumber whenever possible. This choice aligns with the durability and resistance found in the original slow-growth wood.
An illustrative example is Southern yellow pine with 80 old rings, showcasing its robust nature compared to the mere 7 rings in newer alternatives.