At 12 hours a day, the 6550 tubes in the power supply will need to be replaced at around 5 months. (2,000 hours.) The remaining tubes (6H30) will last about twice as long.
Audio research reference 10 tube replacement
If I use this preamp 12 hours a day how long Will it take before I need to replace tubes?
I hear Macintosh preamp tubes Will last 9000 hours. Don't mind replacing a couple tubes but very expensive to replace all the audio research tubes.
Otherwise looks like a nice preamp