Originally Posted by merlinextraligh

Doing 2x 20's, 3x20's, 4x15, 5x10's you are working the same system as doing a 1x40 or 1x60.

The psychological cost of doing a full on 1x60 on a recurrent basis is too high IMHO. You can do 2-3 days of 2x20's in a week. If you really do an all out 1x60, it's likely to cook you for a week.

Also, I'm willing to bet if you did 4x15's, your average watts for the 15 minute efforts would be higher than the 1x60. Thus I think you get more advantage by being able to pull your FTP up a bit.

As for familiarity, and pacing, if you've never done a 40k, I could see the merit of doing one in training. However, I think you're going to get a pretty good idea of what's involved and appropriate pacing from 20 minute efforts.