This dumb lack of self-will "I'll just obey and do as I'm told" when it was obvious that he didn't need to wait until he was a century old was... very disappointing and lackluster.
And upon getting outside into the world and seeing humans again... He just fucks right off back to the Elf Shire where the elves living in a boring-as-fuck paradise.
He didn't even so much as question the elder elf, "Hey, I'm obviously more capable than you thought, how about I leave now?". Nope. Just... continue spending more time in the village. Because reasons.
And you meet a slave girl that wants to learn magic? Well, fuck that, you need to go back to the elf village to read for another decade when you're already likely the most powerful elf. I mean, gee, it's not like she wouldn't go back to being homeless, hungry and just kidnapped or enslaved again.
Good premise, but very generic and the MC went waaaaaaay too fucking native and drank the elf Kool-Aid. Which is probably some sacred tree sap or some shit, you know how those knife ears are.