Depends on how you're training dude. I'm literally murdering the hell out of my muscle groups in the gym now, so from what I've read and been instructed it seems that a max of 4 hits a day is what actual size trainers need (because they destroy so many muscle fibers). When I say 'murdering', I'm basically piling on the weight, going through around 6-8 reps and then being spotted slightly. I only stop lifting the weight when my muscle(s) simply can't take anymore and they're screaming. I'll stop lifting when I literally 'can't' lift anymore lol.