How often does this amp need to be biased and is it possible to affect the biasing during (careful) transport? I had my amp serviced shortly after I got it and have now had to bias it again a couple of times since (maybe 3 times in a month or so). Is this normal or is it possible something is going wrong with the amp? When the tech changed the tubes, he mentioned they looked like they had been overheated\overbiased, causing them to fail and I want to be sure there isn't a fault somewhere that may cause the same issue to happen again (I bought this amp used). If it is normal or tubes require some sort of "settling in" period, then cool - maybe I'm just being paranoid... Thanks for the help.