Re: Frequency of Confession
Canon 989 states: "After having attained the age of discretion, each of the faithful is bound by an obligation faithfully to confess serious sins at least once a year." It can be logically concluded that "serious" means "mortal" sins in this context. The second paragraph of canon 988 states: "It is also recommended to the Christian faithful that venial sine also be confessed." Note that this is a recommendation and not an obligation. So your priest friend is correct.
Fr. Vincent Serpa, O.P.