Do you start fine tuning the system with cables or tubes ?

 Better NOS vintage signal tubes should last 5000 hours or more, especially from 1950s and military/industrial grade. Some vintage power tubes can also last for thousands of hours. Problem is availability of some of them from reputable sources.

But tube equipment, especially power amps, is for those who want to be involved. Like high end tape decks and turntables. Reward, besides the involvement , is great sound.

"Better NOS vintage signal tubes should last 5000 hours or more, especially from 1950s and military/industrial grade. Some vintage power tubes can also last for thousands of hours."

This depends upon the unit/design the tubes are being used in...

Certain designs from popular manufacturers are known "tube eaters" (CJ, AI & AR come to mind, but there are others as well - like Cary/Carey? and SF).

DeKay

DeKay, of course.

@audphile1 

"And dumping money into tubes with today’s prices, you are more likely to get better ROI out of component upgrade."

You're talking in absolutes; I just don't see it.

Nor do I. You get the most out of your system without major upgrades and only then move further if you are so inclined. But not $5k tube set for $3.5k integrated, no, that would be too extravagant, I got $1.5k tube set in it.