I’ve always said if you’ve never missed a flight you spend too much time in airports. Usually the cost to miss a flight is relatively low but if you’re showing up early, each and every trip, you need to add up all that time… it’s a lot.
There are times when the cost of missing a flight can be much greater — like when you’re trying to fly from Australia to the U.S. and there just aren’t a lot of flights. And when you’re doing it on an award ticket in business class. You really do want to show up on time.