NOS Transistors and Tubes Always A Good Thing?

[DreadPirate]

Generally speaking, even when a brand new equivalent is available, will NOS transistors and tubes be a better choice? Capacitors can dry out, so those, I'm not unsure about. Can transistors or tubes degrade over time even if unused, and if so, what is the mechanism? Certainly modern production and engineering practices result in better reliability and longevity in the case of these two?

[SY]

Oh, yes. Over time, tubes go gassy and eventually, even silicon degenerates (though not as quickly nor as dramatically). I mostly eschew NOS silicon because the new stuff is so much better; my one exception is cheap LEDs, which were dimmer in the old days, but tended to have lower AC impedance.

I only buy NOS tubes when they're of a type no longer being made. And even then, I overbuy since I know there will be some early failures.