Took me forever to stop using the orange crinkle comb that came with my first kit, legit three years before I grabbed a proper fine-tooth.

But wouldn't you say those older appliances could be dangerous with exposed wires and no safety features? A lot of that old stuff wasn't built to handle modern electrical loads or run for hours like we do now. Plus the newer models use way less electricity and are a lot lighter, so you're trading some durability for safety and efficiency.

Rubys80, the beaten up box thing is so real. I got a high end espresso machine once for like 80% off because the corner of the box was crushed. It looked like someone dropped it off a truck but the machine inside was absolutely flawless. It's actually kind of funny how scared stores get of perfect items just because the packaging took a hit.

You mentioned "cold solder joints" which does sound like a preheat issue, but that "3 count" thing isn't really a standard fix for that. Cold joints usually come from not heating the pad and lead evenly, not from the overall board temp. Letting the iron sit a little longer helps but it's more about making sure both surfaces hit the melt point together.

Did you try checking if your interface's preamp was just running hot that whole time?