While it's still not a good idea to spill drinks around playing cards, I think if someone spilled a drink, you'd much rather the cards be sleeved. It is a bit harder for the cards to get wet, and fewer cards will get soaked, and with a new sleeve a soaked card isn't totally unplayable anymore.
I know some people who double-sleeve their cards in order to fully seal them - they use a penny sleeve inside a real sleeve. Not sure if that works with commonly available Euro size sleeves, but maybe it does. Not a huge deal for me, really.
I ended up getting 500 sleeves, so I can sleeve all my Base Cards, plus then I'd have enough for up to 11 Kingdom cards, all the Ruins, and a bunch extra in case a clumsy player rips up a sleeve when removing / adding cards to them. In many cases I could sleeve two Kingdoms in advance to speed things up a bit too. I'm going to try and see if I prefer playing with sleeves enough to invest in the Hobby Lobby box, wood dividers, a dremel, etc. Maybe I can make use of dramatically inefficient resources and 3D print dividers for the box.
Thanks for your help everyone
[Edit: I don't see the point in sleeveing Events. Who cares if my cards are damaged, they're not collectible. The only reason damage matters is if people can cheat and track their deck via card damage / if cards get gross and stick together, which don't apply to Events]