to burn fat? it may well be wasted time. If to get into "fight condition" then it serves a purpose.
The two best ways to do cardio for fat burning that I'm aware of are...
1> HIIT (done for 15 minutes) to get you into an all day fat burning mode. If you can go longer, then you didn't work hard enough. If you can't make the 15 you worked too hard.
or
2>Lower intensity, for up to an hour, first thing in the morning before breakfast while glycogen stores are lowest. That way you are working on stored body fat rather than glucose (and glycogen converted to glucose when glucose stores are burned up).
Two sessions a day isn't going to be MORE effective than either of those for fat burning. Been there, tried that. Got down to the size L Tee shirt.
Remember too, fat burning is like all other results...it's done in the kitchen. Eat for the results you want.
Good luck to ya. Need more specifics just ask and someone will try to help you.