I have found 2 times a week at the bench doing a hard day with 5x5 and a 80 percent day with 5x5 works best. While also overhead pressing with the same variables as above. You want to make sure all heads of shoulder and cuff are being overloaded to prevent weakness. The bench does work the superspanus and other 2 external cuff muscles like the overhead press. Also remember the bench is the hardest on the shoulder and causes the most inflamation due to eccentric movement. Shoulder impengment also happens easyer since the scapula is not moving upwards like during a press. Mind you this doesnt mean the bench is bad, but need to be programmed smarter then other lifts in my opinion.