The aging of components. Your experience and knowledge...

All my stuff will last at least 30 years because i have world class stuff.

Velodyne Sub, 12" cone replaced by me, surround rotted.

Tubes, last a heck of a long time, perhaps 10,000 hours, so, how to have confidence?

I finally got my own tester, little one, then a big Hickock. Little one as accurate as big one re signal strength, shorts, matched pairs or quads (check what you buy when received).

Different tube types/brands sound different: YES, research, don't go crazy, buy from source you can exchange if unhappy after 60 hrs burn in, i.e. Brent Jesse ...

https://www.audiotubes.com/

I have and have used much Vintage tube equipment. I believe in keeping the old stuff going, especially family heirlooms.

Repair, Yes, Thoroughly Check during a needed repair, yes. Overhaul/Upgrade Kit, No. Acquire Spares!

How hard are they pushed? i.e. Volume/Noise

If problem occurs, I have them ’fixed’, something specific, while in the shop checked, i.e. ’overhauled’, but never ’upgraded’ just because they could be.

Mono Tube Amps (fisher 80z, new 1958). A few resistors replaced, once by expert, once by me. Still sound terrific 62 years later. Full volume, dead quiet. On the shelf now.

Mono Tube Control Center, 1958, with FM stereo multiplex added. Not used since 1978, sounded great for 20 years, full volume, on the shelf now?

Tube Receivers: Fisher 500C (3); Fisher 800C (1, same as 500C, but add AM band as well as FM). Bill has 1 500C we traded, others on the shelf. Those all got noisy if volume past 50%, never needed that much with my efficient horns.

Tube Tuner/Preamp, current, McIntosh mx110z, 1962. No sign of upgrades before I got it 2 years ago. Like the Fisher receivers, noise begins at 50% volume, again, which I never need. Best sounding FM Tuner and Phono Stage I ever heard/owned. R2R tape also sounds terrific. It will have a full overhaul/upgrade sometime, by Audio Classics, near their headquarters

https://www.audioclassics.com/

Drivers from 1958: 15" woofers. Cone and Voice Coils replaced professionally once, cones only replaced by me once. Treated cloth rings, they last much longer than rubber or foam, cones dried out, pin holes.

Spares: 1 80z, 1 15W, 1 mid horn, pair of tweeter horns.

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Solid State: very minimal work needed over the years

McIntosh MC2250. LED light replaced. Factory checked, all still good before I sold it 2 years ago.

McIntosh C28 Preamp. Low level inputs only: noise past vol. 50%, Poor internal ground connection. Repaired prior to sale 2 years ago.

I have a bunch of em here in Seattle. I'd be willing to trade two floating and one Narrows for your one in NYC.