I have been using the front snorkel for only a few weeks, I have found it to be helpful with drills. I generally do a lap using it, focusing on a particular point then remove it and repeat a lap with the same focal point. I use the standard Finis, tried the Freestyle but I am not advanced enough for it yet and get H2o in it too frequently.
I too had some concern about depending on it but I have not found it to be a problem. I actually don't like using it for full stroke because it tends to wobble even at my slow speeds!!