Cardio five or more times a week does not have anymore benefit or speed in the process of burning fat than 2 or 3 times a week, in most cases. With too much excess cardio, there might also be the danger of lossing muscle mass along with fat. Twenty to thirty minutes duration of cardio training should be just fine for most folks.
Interval training (12-20 minutes total length) can give greater results, by far, over any standard cardio session between 30 t0 60 minutes or longer. Tabata training comes to mind as one of the better methods. 20 seconds max effort, rest 10 seconds, 20 seconds, rest 10 seconds, etc. usually between 5 to 8 sets max. Other like interval programs out there, if you care to do a search. HedgeHog presented a good interval program a few weeks back, if you can find it. Good Luck.