when i first started smoking way back in the day, the guys that introduced it to me told me to take a hit or two and pass (the pipe then, phx now hah) but they told me to hold it in and try not to exhale until the piece comes back to me. now that was a kinda cool learning tool and i thought that holding in your hits was the way to go...but maybe not that long. now a days when i puff puff pass, i take the hit, take another little breath of air in...hooooold it in for about 3 seconds and then exhale. i figure anymore than that is just smoke irriatating my insides. so go along and hold it in but i dont know if it will get you much but coughing more often. just remember to take that extra breath in after the initial hit because i think thats important to really hold your hit in your lungs good and tight and less more about how long you hold it in.