I have had the amp sens Aug 09 i have the sovtek power tubes in it now and one will not bias. But i have had three quads of the gold lions from guitar center(they ship the tubes with no extra packaging) and they never lasted more than two to three months. I run the amp about 10 to 12 hours a day.I am looking for a good place to get the eight gold lions & four sovtek's tested, seams when they go they like to take the rectifier with it.(I'm getting very good at rebuilding the copper caps). So i ordered kt-120 and I'm hoping that they will last longer. I have a 1951 st-70 that has tubes that are older then me(1953)that plays out in the shop.So I'm wondering how long do the power tubes last on average in a st-120 at reasonable to reasonably loud play? I have Denon avr 3806 as the preamp and crossover 95Hz to sunfire CRM2s as the mains on the st-120.