It is never a good idea to attempt to "eat back" the calories you have burned through exercise. This is because it is impossible to know with precision exactly how many calories you expended during exercise. All cardio machines give inaccurate and exaggerated estimates of calories burned because they are calibrated to the "averages" (when they are calibrated at all!) and not to the individual. Meanwhile heart rate monitors, the FitBit and BodyMedia type devices also tend to yield inaccurate data depending what type of exercise you are doing and precisely how you are wearing the device.
Studies done in laboratory settings with the most sophisticated devices and controls have shown again and again that the typical female burns only about 200 to 300 calories during 1 hour of intense exercise. This is the equivalent of about one cookie! It is hardly enough to worry about trying to "replace". Trying to guess at how many calories to "eat back" after exercise can easily put a large dent in the deficit you've worked so hard to create.
You should avoid the temptation to think of exercise as a calorie burning tool. It is very easy to overestimate how many calories you may have burned during exercise and even easier to underestimate how many calories you are eating to adjust for exercise expenditure if you begin to engage in the dangerous practice of exercising to "earn" more food. This is because excessive exercise tends to drive hunger at subclinical levels, leaving you exhausted, less active throughout the rest of the day and feeling deprived.
The only thing we can measure with reasonable accuracy is the amount of calories we put IN through eating. The single most important component to weight loss is caloric restriction. Try to start thinking of your dietary compliance as your main fat burning tool and your exercise activities EXCLUSIVELY as muscle building tools. Think of any calories you may have burned during exercise as icing on your weight loss cake. :)