O.K., confession time: I've owned my 1994 Matchless H/C-30 since 1996, and I've never changed so much as a preamp tube. Some are NOS (GE rectifiers), all seem to be little glass bottles with glowing wires in them. Sad to say, but my ignorance really is that profound. I know they're in there, and every time I turn the amp on, they light up and commence to do their job. I've never given them another thought. Now, I'm not one to sit around worrying that the sky is going to fall on my head, but I'm starting to wonder if I'm missing something. The amp sounds so good, I'm not sure I'd notice an incremental decrease in tone quality. Catastrophic failures aside, what would be the symptoms of tubes that are just plain too old? I'm sure if I allow myself to think about this too much, I'll get paranoid and have to do something, whether there's a problem or not. Might already be starting down that road. Cheers, Rob p.s. Any other lazy sods out there who can't be arsed to change their tubes?