anyone considering this (or any other big dream in your life) - do it! make a decision, start riding longer distances, join audax uk, become a super randonneur, join your local cycling club, do some speedwork - getting fit is fairly simple (and easy if there is motivation). go after your dreams, it's never too late. my dad started cycling only last year at a young age of 61 and enjoying it immensely, got himself two carbon bikes (summer and winter), rode a 100 miler already and talking about the mountains now!
be bold, be determined - the world is your oyster