I've had mine for 4 yrs now and sounds the smae as the day I turned it on. I don't know much about biasing. I guess the tubes have 2000 hrs, but as I say they sound like the day i turned it on. btw I use the bass and treble tone controls up 98% of the throttle. What I've found the tone controls have basically 2 modes, off/on. Only at 90% open do the tones open up, at 95% open there is some slight notice. At 98% is the only way I like it. I love dynamics, and anything less is not acceptable. Also at mid open on the tone the amp sounds very flat and lifeless.
So i guess if you bias from the inside, you get the same effect as pushing the tone controls up to 98% open. Only at 100% do i gut a hum from the amp. btw I lsiten at low volume, 1/4th to 1/3 vol open. After 1/3 I get much less stability /dynamics from the amp. Maybe the speakers are too much a load against the currect for the amp. The speakers are rated 87db. . But still, at 1/3 vol open, i get plenty of music to fill my 30X40(with open hall ways on everyside) cathedral ceiling room. The music carries throughout the entire house. So maybe with low vol I use the tubes will get a longer life. btw Pierre mentioned the Jadis stock tubes are quite expensive, so replacing will be a major cost. Which i have no plans to do for yrs to come.
