well many sell their gears anyway regardless....when the sawa factor sets in, then that is it...
plugging in and unplugging tubes, loosens the sockets, corrosion sets in and gas tightness is compromised...
in the old days, tubes are replaced only when they have gone bad.....
you do not just mess with your tube amps when they are running fine....
when that inevitable sawa factor sets in, then you can sell your tube gears...
that is why i recommend to those that seek my advice to have a pp and set tube,
and solid state amps as well....rotating these amps will give you variety.....
ask Dana, he has a lot of various types of gears in the house, brimming to the seams....