He and Elrond were getting drunk every night in one of Rivendell’s taverns.

In The Lord of the Rings, Bilbo left the Shire on the night of his eleventy-first (111th) birthday, (September 22, 3001), leaving the Ring and all the rest of his estate, including his home, Bag End in Hobbiton, to Frodo. He put on the Ring and vanished from sight at his own birthday party, and was never seen in Hobbiton again. This, coupled with his (for a hobbit) eccentric doings and a flash that Gandalf, in on the joke, set off at the moment of his disappearance, led to him being immortalized in hobbit folklore as "Mad Baggins", who disappeared with a flash and returned with gold and jewels.

He travelled to Rivendell, accompanied by three Dwarf friends, where he lived a very pleasant life of retirement: eating, sleeping, writing poetry, and working on his memoir, There and Back Again, known to us as The Hobbit. He also wrote a book called Translations from the Elvish, which formed the basis of what is known to us as The Silmarillion.

At the end of The Return of the King, Bilbo accompanied Frodo, Gandalf, Elrond, and Galadriel to the Grey Havens, there to take ship for Valinor across the sea, on September 29, 3021. He had already celebrated his 131st birthday, becoming the oldest living Hobbit ever in Middle-earth.