Since this program won't make you hurt or tire you out, the only other excuse to skip it is the time it takes. Now 15 minutes a day isn't much time, even if you ignore the time you gain by not dropping dead prematurely. But the effective bite out of your day can be reduced even further. More than half your exercise time is spent in the run and jump exercise, especially after you advance to the middle rungs of the Lifetime Ladder. I've found that, with a little practice, I have no trouble keeping count of the 75 steps and 10 jumping jacks while letting my mind free-run on whatever I'm interested in at the moment. In fact, in the couple of years I've been following this program, I've had some of my very best ideas while doing the running and jumping exercises. I don't know whether it has something to do with getting the circulation going, or just with being forced to think for five minutes or so, but it happens. (It is hard to keep track of the number of sets of running and jumping at the same time. That's why I recommend using coins or other markers to keep count, freeing your mind for more interesting pursuits.)
Further, the time required remains pretty much the same as you progress from rung to rung. Since each rung calls for more repetitions of each exercise this might not seem to make sense, but as your conditioning improves you'll find you're performing the exercises at a brisker pace, keeping the total time roughly constant. If one exercise seems to take forever to get through, that's an indication you've moved up to that rung too quickly.