This song, written by Paul McCartney, was on the Beatles' Sgt. Pepper album. It was released in 1967. I was 21 years old at the time. And yes, back then 64 was definitely "many years from now." When you're 21 (and especially in 1967) being 64 years old seems very nearly unimaginable.
Life goes on though, doesn't it? And tomorrow morning at approximately 6:20 a.m. the unimaginable will become my reality. So, "will you still need me, will you still feed me, when I'm sixty-four??"