There is no doubt that prolonged, continuous endurance work can contribute to fat loss. If you like it, and you have the time, it's definitely a valid option. Personally, I don't like that kind of exercise any more as I find it too long and tedious.
The other issue with any kind of endurance workouts is their 'side effects' on whatever other training goals you are pursuing. Too much continuous aerobics tend to interfere with efforts to gain muscle and strength - particularly higher intensity work... too much running in particular can kill muscle building progress. The reasons behind this aren't fully understood, and how much is too much varies widely among individuals. Many report that HIIT work interferes less with muscle gain, others feel that large amounts of very low intensity aerobics is the least interfering. This issue is difficult to quantify and study, so there aren't any really solid guidelines. For me, the worst is very high intensity aerobics, like fartlek runs, tempo runs, or VO2max intervals. If I do one of these, I can see it in my strength performance the very next workout.