If youre looking for exact precision, roid cycling will dissappoint. Like steve said, you have to be flexible and open to adjusting "on the fly" during a cycle. Another important facet is knowing your body and knowing when a cycle has "run out of gas". If youre set to run a 16 weeker and your cycle just hits the wall at week 10 then know when to quit while youre ahead and not waste the rest of the gear on a cycle that, for all intents and purposes, is finished. I know easier said than done when all you can think is "if i just pin for one more week it will turn around". Very easy to get psychologically addicted to something like roids