I've been on holiday for over two weeks (including running the New York Marathon!) and only just set up ,my third 620 this morning.
I'm hoping for an improvement but I'm not optimistic. The prior ones occasionally found a signal immediately but 5-6 minutes was the average and sometimes over 10 minutes. Not nice in the winter when you're standing shivering waiting to go on your run.
I remain of the view that these are great devices when working but that Garmin flood the market with shoddy products with little visible effort to improve well known faults.