I would have thought that most folk should be able to judge by 500ft whether or not it is going to be a success.
At the strip I'm based I fly all circuits at 500 feet or below. Most approaches are glide approaches. Do I always make a perfect approach? No. Do I sometimes have to use the engine? Yes.
Clearly, this shows that I'm a very average pilot, but then most of us are and it is very easy to screw up a glide approach from 500 feet.
Really, I'd say there are two phases to the PFL:
1. Positioning yourself to a good position at 500 feet
2. Getting in to the field from 500 feet
Neglect the second at your peril. The world looks and feels very different below 500 feet on a PFL -- best not to learn just how different in anger.
QDM