In the old, old days, the amplifiers designed by William Zane Johnson, founder of ARC, were well known to run the tubes very hard, and failures were common. To deal with this issue, ARC was known in those days to "update" their amplifiers quite frequently. I never knew whether they were trying to convince customers that the newest version of whatever amplifier was "fixed" or what they were really doing. But tube failure, sometimes catastrophic, was a price you paid for great sound. In any case, Mr. Johnson has long been out of the ARC design picture, and I have not heard in many years that modern ARC amplifiers were particularly unreliable. If you know what you are doing with bias adjustments, you could source the tubes from Tube Depot, or one step up the scale would be to buy selected tubes from Kevin Deal or Jim McShane, which might cost a bit more but those guys really do test the tubes before selling them. Even the latter sources might be less expensive than buying tubes from ARC. Then you can start at bias point where the plate dissipation is at first low-ish and let the tubes break in for several hours before turning up the current, if indeed the tubes are stressed in modern ARC designs. But Tube Depot is a reputable source, far more reliable than eBay might be, for example. Keep in mind that tubes age and change parameters over time, no matter who sold them to you. So, long term, there are no guarantees regardless of source.
Yes, marktomaras, ALL tubes will require re-biasing once in a while over time.
