1. How often is there a leap year? (Every fourth year.)
2. How often is there a flight to Shanghai?
3. How often do you write to your parents?
A: I've been having bad dreams lately.
B: Really? How often?
A: Just about every night.
B: What do you dream about?
A: I dream about being in a boat and suddenly a storm comes and I drowned because I can't swim.
B: Maybe you should learn how to swim. Then you won't have any nightmares.