I have had my Ref 110 for about 5 months, and have about 550 hours on the tubes. Over the weekend, I decided I should check the bias, which is VERY easy to do. It was still very close to original spec, at 65 mv DC. I only moved adjusted one, and that was off at 61 mv. Very impressive performance. That is why you spend extra and buy the ARC tested and burned in tubes...
Yes, at 2000 hours it is probably time to change the tubes.
Yes, at 2000 hours it is probably time to change the tubes.