To mod, or not to mod...Classe CAP-151?

What do you hope to achieve? You might be better off selling and upgrading.

I agree. If you're dissatisfied the CAP-151, sell it. I've done modest mods to Classé components. IMO, the CAP-151 is not a candidate for worthwhile upgrades/mods.

Actually, I am quite satisfied overall and was thinking more in terms of extending it's longevity. Perhaps the old adage "if it ain't broke..." applies. Thanks for your thoughts Brf and a special thanks to Gbart, for his help with the binding post upgrade.

The best you can do to extend the longevity of your amp is to just not abuse it. The electrolytic caps will dry out and eventually need to be replaced. Opinions will vary widely but my personal opinion is that you won't reach that point until the amp is at least 20 years old, maybe even 25 years.

Apart from the obvious do-not's: overheat/expose to high humidity etc. or what IMHO, is the ultimate form of abuse...STORAGE, what otherwise constitutes abuse?

Apart from overheating, avoid very dusty locations and do not short the outputs. The CAP-151 does not have any fancy output protection circuitry, and relies solely on the positive and negative power supply rail fuses to blow and protect the output transistors.