Maximizing FAT loss with LOTS of Cardio? (Xpost from Main Board)

Is there a limit to how much fat one can loose by increasing time spent doing cardio (in the correct fat-burning heart rate range?) In other words, does the body keep burning fat as long as there is still fat to burn when it is exercised (cardio) in the fat burning heart rate zone?

I'm wondering how much more fat I can loose by upping my cardio. I'm willing/able to do cardio for 90-120 minutes 5 days/week.

For what it's worth, I just did a VO2 sub max test which tells me what heart rate I need to work out at to maximize fat loss. I was so happy to see my results because the test is showing that I don't have to work out nearly as hard as I thought to loose fat. In fact, my fat burning pace is a heart rate of 105-112--this is even lower than the standard HR calculation (220 minus my age, times 60-65% or 80-85%) which for me was 135-140 at the low end to  158-163. So I can comfortably exercise for a while at this heart rate without getting too tired.

Please note--I am aware of the benefits of strength training  and I do this kind of exercise as well.Just was trying to focus directly on fat burning with this question.