I agree with a lot of folks here the longer you can sustain your W/O at a lower level perhaps the longer time you are in that fat burning mode. Yet the High interval training is something that does wonders for me too. It is really hard becasue to are going to a really high level of exurtion (sorry about the spelling) and then down so fast only to turn around and continue this pattern. The time sure does fly though.

Good luck. I think what you are doing is great and if you have the extra time do a little more

Daisy