I reckon I don't understand what the problem is. If you're getting enough exercise to burn the calorie goal you've set up, then it doesn't matter if it takes you less time. Like, if you originally thought you'd burn say 1000 calories by exercising two hours 5 days a week..... but now you find that you can actually burn 1000 calories by exercising only one hour 5 days a week. Well, there's nothing wrong with that.
While we can get Spark Points for up to 120 minutes (2 hours) of exercise, we don't have to exercise 2 hours a day. The important thing is the calories burned.