I don't mean to come across contrary, but the body doesn't burn less fat as it adapts to cardio. Although it may seem easier to complete the cardio session, as long as the intensity is the same, the same amount of fuel will be required to perform the muscular work.
In fact, as you adapt to cardio, the body will decrease the amount of time it takes to mobilize stored fat and the muscel tissue will increase its ability to burn fat, thus sparing carbs and muscle glycogen. In essence, you because a more efficient fat burning machine.
Would it make sense to cycle cardio? I guess it depends on why you are doing it. If you are doing it to burnf at, it would not be a good idea. If you are wanting to cycle your cardio because it is interfering with performance (muscle power and quickness) then I would say yes, you should gefinately cycle your cardio based on the competative season.
