the more air-sacs you fill with THC (the high causer) in your lungs and the longer they saturate the pores the more THC that is penetrated into your system and therefore the higher you get. it is definately true that the longer you hold it the higher you get and the deeper you get the hits in your lungs the higher you will get. sometimes i hold it in so long i dont even have any smoke to let out when i exhale...