Just as your body adapts and becomes more efficient in your resistance training routine (SAID principle), you body does the same in your cardio program. Stage training can help continue the cycle of adaptation, but what about other variables?
Creating variety can be as simple as changing your form of cardio every 4-6 weeks. You can chose specific programs that target certain aspects of your goal (not spot reducing). For upper body development combined with cardio training, swimming is great. Need more leg and glute power and development? Try running hills or adding an incline to the treadmill. Rowing is an amazing way to improve back and shoulder development.
By combining Stage training with an organized cardio plan, you can create optimum long term results.