Noob question: will mining ruin my hardware? I know if it gets too hot (~80C IIRC?), it can damage things, but what if i keep it under that threshold and just mine nonstop? Monero specifically.
Barring a unit that was defective in the first place, running at 80 C shouldn't damage a typical video card. For a lot of cards (especially from before the newest generation of cards which have had a lot of emphasis put on efficiency) that's a completely normal temperature. It's not till you hit 90 or better that temperature can become a problem for certain cards. On any card made in the past couple years, their coolers are good enough that 90 C shouldn't even happen unless you've got bad airflow. Older cards can usually go higher than that, and it wasn't that long ago that running an r9 290 at 95C was completely normal, but you shouldn't be mining with those cards unless you intend to use them as space heaters.
It's a common misconception that computer hardware performance can degrade over its lifespan, but that's only true of hard drives. (And even then it's more likely bloated old software slowing it down than the disk itself). For GPUs, the only thing you might break from mining are the fans, but those are cheap and easy to fix.