Immortals would be insufferable. 97% of my conversation topics are pop culture references from the past 40 years. It's already difficult to talk to people a couple decades younger than me. Imagine if I were 420 instead of 42. Everything that happened in every moment of every day would remind me of a story nobody cared about or wanted to hear. Jeez, that's literally the problem with the elderly!
And you think it would be cool to be a vampire? Insufferable.