When I was talking flying lessons and instructors were emphasizing the importance of understanding potential weather problems, we were given the following slogan - "It's better to be down here wishing you were up there than up there wishing you were down here."

Applying that philosophy to the question of the thread - I'd rather be there wishing I had left later than on the road wishing I had left earlier. For me the compulsive worrier, I would add 30-60 minutes to all of the above times for an international flight.