Another silly post with a simple obvious answer.
If you can’t hear any difference why change the tubes???
You gain nothing.
But by all means keep a spare set waiting for the day.
yes this is generally sound logic with most tube amps but arc tube amps run the risk of needing a repair to bias resistors and/or the circuit board area near it, if a power tube has a ’hard fail’ - despite the wonderful sound of these amps, this is one of the issues arc amp users face, and thus, typically users replace tubes before they are close to being totally shot
I would contact somebody like Upscale Audio or Brent Jesse let them know what type of system you have and the tubes you are currently using and let them recommend some NOS tubes not only will you be replacing your tubes but you will also experience a much better sound.
nos power tubes are not a practical option with modern arc tube amps - we are talking modern day kt120 or kt150’s which the amps are tuned for driving, for maximum power and transparency
but kevin deal or jim mcshane will sell you properly screened and burned in sets of these for the ref110 upon request - there were shortages of these through last year when covid hit but as of late in 2020 supplies started catching up
