【Often】 , 【frequently】 , 【oft】 , 【oftentimes】 may be used with little or no distinction to mean again and again in more or less close succession.
But 【often】 stresses the number of times a thing occurs, without regard to the interval of recurrence; 【frequently】 usually stresses repetition, especially at short intervals.
【Oft】 and 【oftentimes】 differ little from 【often】 ; 【oft】 , however, is used chiefly in compound adjectives or occasionally in formal discourse and 【oftentimes】 is occasionally preferred for intonational reasons.