Actually, it was 3 - 4 months! :banghead:
It doesn't seem to have effected anything, but it sure didn't help anything.
With that little current keeping the heaters warmed up, it probably wasn't much different than leaving a stereo on for months.
The only reason it happened is because my Gibson Goldtone has it's knobs on the back of the amp, and there's no jewel light. It has a 3 position switch On/off/stdby, and I must have walked away thinking it was off.
It's an amp that I rarely plug into, and it was plugged into the wall.
I was mortified when I noticed it, knowing I hadn't used it since early Spring. :scared: