Dozens of tube components later, the only ones I ever had concerns about a warm-up time longer than (say) 15 minutes were the hybrid electrostatic amps with lots of high-voltage transistor CCS on their outputs.
Never really experienced that with any pure tube components. They should sound really good very quickly. Unlike transistors, tubes need heat to operate at all, and they have filaments for that very purpose - which efficiently heat up so the tube operates at spec very quickly. Transistors are however affected by heat, and can take a relatively long time to reach their final stable operating temp - because heat sinking is used to pull heat out to keep them at a safe operating temp under maximum load conditions. There’s no such heat tug-of-war with tubes, so they get stable quick.
The only aspect of tube amps that has a slowly heat-accumulating element would be the transformers, and maybe silicon rectifiers and voltage regulators in the PSU. Though only large transformers should take hours to fully warm up. I don’t know if that significantly affects their performance - maybe. That could be the "4 hour warm-up" in your case.
