Anytime I ever make burgers fresh I always try to flip too soon. With the premade frozen ones it doesn't matter, you can flip those all day long, but with fresh made patties if you flip too soon the charred top layer comes off and stays stuck to the grill. Of course, if you don't mind sacrificing one burger as a tester for all the other ones, this is fine, plus you can scrape the delicious charred crispy layer off the grill with your spatula and have a snack while you cook.
I'm really terrible at cooking burgers though, I've never been able to figure out a charcoal load /temperature that lets you get that crusty outside without starting a grease fire.