I hit my muscles twice a week (except legs because of time and schedule constraints and also fuck legs). chest&back, shoulders&arms, legs, chest&back, shoulders&arms, rest, rest, repeat.
I can honestly say that I do not ever count how many sets I'm doing or care about that or think its relevant at all... but if I had to count them I suppose I do about 10 sets total for each muscle group, each workout (so 20 sets per muscle group every week).
3 exercises for every upper body muscle (flat bench, incline, db flyes, pullups, bb rows, tbar rows, seated military, side raise, rear raise, bb curl, db curl, reverse curl, cgbp, db french press, pushdowns, if I ever actually had time to train legs it would be squat, sldl, leg extension, leg curl, seated and standing calves but normally can't because of PT and physical testing right now...)
It's no problem at all and if I were gaining weight I would do more sets (not because the number of sets you do is magical or relevant, just because I would have more energy and would probably feel like going heavier) and maybe another exercise or two.
I personally feel that a higher frequency is preferable and I highly recommend it because it allows you to get good at the BASIC traditional bodybuilding exercises by doing them often which is where the real size is at IMO.