Holding your hits is sometimes good to do but always bad, if that makes any sense. lol
IF youre smoking good shit it take longer to absorb all of the THC. If its shwag or mids a few seconds will do
edit: oh yea, its always bad because youre allowing more time to absorb carcinogens and tar in the smoke. Its not as bad though if its high grade because theres less of that bad stuff