NOS vs used tubes


I've enjoyed my tube gear for sometime now and never paid much attention to it, just enjoyed the music. I've started to listen more carefully and have decided to investigate the finer points of tube ownership. ( which is probably a mistake) I'm interested in doing some "tube rolling". I'm not sure paying a premium for NOS vs good used tubes makes sense. Is there a sonic difference if a used tube tests out to 70-90 % of the new one? Or is it strictly a longevity issue and one gets the extra hours out of the NOS? Is it a matter of hours vs. dollars and NOS buyers chasing something that's not there.

Any thoughts would be appreciated

John
jfh
I have no preferences for new v. used. The only thing I look for is that the tubes are closely matched. A set of "marginal" to "good" tubes that are matched sound a lot better than a set of strong tubes that do not. Also, some tube gear works best with what the manufacturer provides you with. I have tried many a tube ($$$) in my CAT preamp and have always gone back to the batch Ken sent me.
I would suggest contacting Andy Bouwman at Vintagetubeservices.com He will deliver you some of the most straight-shooting, best-informed, non-BS opinions on the subject.