Depends how fat i am.
If i was to get up to 20-25%, i'd do a long one down to at least 15%.
Otherwise, i barely go over 6-8 weeks dieting. I'm not competing so there's not much point.
Besides, with my biochemistry, i've a tendancy to hold fat and lose muscle too easily, as well as gain fat and not much muscle easily when bulking, so i tend to do short durations of both.