Me too. I have a quad of Gold Lion KT 88 and they have a lot of hours on them. A lot …. I took them out of service after about 4 years of hard use and kept them as a back up.
I changed speakers and found that the JJ EL 34 sounded really good . I had a tube that lost vacuum. Put the GL back in.
Fast forward to a few months ago, I got a tube tester and put the KT 88 back in and they are still strong , close to the Apex matching sticker on the tubes.
In an amp they are still tightly matched. Pretty amazing considering how many hours I have listened to them.