Following your suggestion on caps, I did a fair amount of googling on the subject and found a wide variety of opinions on the need and advisability of cap replacement based solely on age. A lot of emphasis on the effects of continuous vs intermittent use, temperature of the unit, etc. The Adcom amps are represented mostly as being quite bullletproof, and some owners report 20-30 years of nearly continuous operation with no significant deterioration of performance. Quite a few comments like "if it ain't broke don't fix it." My oldest/most used amps are a GFA 545 purchased in the late 1980's and a Dynaco 120 (kit) I built in the 1960's. Both seem to still be working fine. Are there specific "best tests" that can be used to determine otherwise or is it just a matter of perhaps unnoticed performance deterioration?