As long as they don't get killed, elves are immortal, right? That would suggest elves see (human) time differently. Assuming humans base 18 on a certain amount of life experience someone should have, how would that affect the age of consent for elves? I can give you my complete train of thought on this, but the question mainly arises from playing Baldur's Gate and the idea that a guy gets caught with an elf, and the cops go: "This girl is only 100 years old. You are under arrest." And the guy goes: "She said she was 300, I swear!" Also, I do not think about underage elves in the shower. Or ever. I'm gonna stop digging this hole now.
I write immortal humans. You are still an adult after 18. I have pairings between million year olds and twenty year olds. It's not weird in my setting. Their memories are cyclical, I think. They remember the past 100 years pretty clear, everything after becomes more hazy. Unless it was a big event. Then there are those who are "enhanced" who remembers everything crystal clear.
I was hoping I wouldn't have to specify... Let's say D&D elves, since I'm basically playing D&D light at the moment. Now that I've double checked, they appear to live to 750 years. Tolkien's elves are the immortal ones. While I'm here, which ones are considered the traditional standard for elves? I don't do a lot in fantasy, clearly.