I am restoring my highly Modified Old Sumo Nine right now, It took a lightening strike a few years ago and I have missed it. In 1983, we put what at the time was a very nice Panasonic electrolytic in the power supply, they were an 85 degree part. It was never turned off for most of those years. While repairing this amp, I figured why not, while its open, I’ll replace the caps... I found nice caps with double the capacitance and lower esr to replace them.... The point is, To my surprise, we measured the old Panasonic caps. their values across the board were still in spec. You just don’t know. My experience has been, that when caps sit without a charge, that is when the tend to dry out. I have never had a cap failure and I do not EVER turn off my solid state gear. (when I owned tubed gear, it was always turned off after each use). I have always been under the belief that it is the charging and discharging caps that is most damaging to them.
