There is NO advantage of holding the smoke in, inless your on a suicide mission.
Your just depriving your lungs of oxygen making you go light headed, the longer you hold it in the more damage your doing to your body.
THC is absorbed in the lungs INSTANTLY, as i say there is no added effect from the cannabis of holding it in longer.
Personaly i dont, i just inhale and exhale.

Take note, this is correct.