From an interview from August 28, 1963 for the BBC (
Beatles Interviews Database):
JOHN: "'How long are you gonna last?' Well, you can't say, you know. You can be big-headed and say, 'Yeah, we're gonna last ten years.' But as soon as you've said that you think, 'We're lucky if we last three months,' you know."
PAUL: "Well, obviously we can't keep playing the same sort of music until we're about forty-- sort of, old men playing 'From Me To You'-- nobody is going to want to know at all about that sort of thing. You know, we've thought about it, and probably the thing that John and I will do, uhh, will be write songs-- as we have been doing as a sort of sideline now-- we'll probably develop that a bit more we hope. Who knows. At forty, we may not know how to write songs anymore."
GEORGE: "I hope to have enough money to go into a business of my own by the time we, umm, do 'flop.' (laughs) And we don't know-- it may be next week, it may be two or three years. But I think we'll be in the business, either up there or down there, for at least another four years."
RINGO: "I've always fancied having a ladies hairdressing salon."
(Beatles giggling)
RINGO: (undeterred) "You know, a string of them, in fact! Strut 'round in me stripes and tails, you know. 'Like a cup of tea, Madam?'"