I read a couple of months back in procycling (maybe feb or march) and i think they interviewed the fdj DS and he said something along the lines of 'train for half an hour longer than the distance of your race'. so
ie. 65km race = 65km + half hour extra once you get to 65.
I guess he is working on the theory that if you only train to the distance you need you will not be a fit as training past the amount you need to race.
I guess it was a bit vague but your question was also a bit vague
