YZ, buried in your post is your question,
"I'm interested to know how many of you use (old scopes) for what you might consider "long range" (relative term)."
Most responders are focusing their responses on "owning old scopes" and not focusing their responses on "long range use" which is your question.
Studies have proven numerous times that we can not accurately judge distances past about 300 yds. That's a fact. Most don't consider 300 yds "long range." What has changed the long range shooting game and requirements for new scopes and new reticles is the laser rangefinder. In the past, the range was guessed and the shooter also guessed on how much to holdover. Both very bad practices. The laser rangefinder and ballistics applications now give the shooter an accurate range calculation so scopes needed to evolve to give the shooter accurate reticle extensions and accurate turret markings to match the accuracy of the laser rangefinder. Can you use an old duplex reticled scope to shoot past 600yds, yes! Will you hit your target? Most likely, no! This is why you need to replace old scopes for LONG RANGE, not because you can still see something through them or they're pretty or nostalgic.
Bottomline, old scopes are not adequate for ethical long range hunting.