The more potent cannabis strains are easier on the lungs than schwag because you dont require as much to get the desired effect, therefore less smoke is inhaled. Another point I would like to make is that I dont care what kind of studies have been done on deeply inhaling and holding in marijuana smoke but i know from personal experience that if I hold it in for 3 seconds i get high, but if I hold it for say....10 seconds, I get tore the fuck up! If your not holding it in you might as well not be inhaling because you are basically wasting the bud. Also there is a little saying you should keep in mind. "Everything is okay in moderation" Too much of anything is bad for you. I wouldnt advise anyone to do it every day.