Often = (1) many times; frequently or in great quantities: The trains are often late.They often go out to dinner. (2) in many cases or instances: People are often afraid of things they don’t understand.
Every so often = sometimes; occasionally: I meet him at the club every so often.Every so often I heard a strange noise outside.
As often as not = quite frequently; usually; in a way that is typical of somebody/something: As often as not, he’s late for work.