Well there’s also the whole “The One Ring is the only thing still keeping the elves’ magic alive, so they know that destroying the One Ring will inevitably lead to the end of the elves” side of things. That’s why all the elves in LOTR are so fucking morbid about everything. The elves rely on magic, and while it did a lot of damage and was undoubtedly evil, the One Ring bound that magic to Middle Earth because it was the same magic Sauron used to appear in Middle Earth. So by helping to destroy the One Ring (and breaking Sauron’s tether to Middle Earth) they’re also destroying the only thing keeping their magic from drying up over time. They’re inadvertently starting a ticking time bomb for themselves.

At least, that’s what I remember off the top of my head. It could be completely wrong, but I’m too lazy to google it.