An hour a day isn't unreasonable in any way. Two hours a day (assuming you can afford the time) is a bit much for your body, under certain circumstances.
The key is what you eat, and how you exercise. If you're on a diet where you have reduced your protein intake as well as your overall calorie intake, then doing a lot of cardiovascular exercise is very bad. The extra calories burned often come from breaking down of your muscle mass, muscle mass you need to keep your metabolism high. If you allow your muscle mass to degrade while you're losing weight, you'll have to eat practically nothing forever in order to keep the weight off.
A better approach is to mix up your exercise, half cardiovascular, half resistence training. And when cutting intake, just cut fat and carbohydrate intake. Leave your protein intake alone, or perhaps even increase it a bit, to feed growth of new muscle (to help raise your metabolism even higher). This will guard against the catabolization I mentioned above.