There was an episode of Sandman on Netflix that addresses this. In the 14th of 15th century, Dream makes a bet with Death that if given immortality a mortal will just get tired of living. Death says, "It's on like Donkey Kong," (citation needed) and she gives some random Englishman in a pub eternal life on the condition that he agrees to meet with Dream at that pub every century. As the centuries roll by, Dream meets with this guy each century and he's never tired of life. Even when he's lost his wife, family, and all his riches he's still not tired of living on the grounds that life is wonderful because there's always something new and exciting coming along.
I can remember the names of my teachers from 1st through 5th grade but I can't remember the names of all the teachers I had in high school or when I went to college.