I have diverted once or twice per year. Mainly driven by the need to fly cross country to get to an aerobatic competition in an aircraft with just an airspeed and altimeter and no stability ie if you take your hands off it will roll inverted.
However, I normally plan my cross country routes via the overheads at airfields so that I can turn back and have a bolt hole if the weather gets worse than forecast. 20-30nm legs seem to work well.
Most times I find conditions to be better than forecast and it would have meant cancelling trips/competitions if I relied solely on the Met.
ZA