Breweries typically drop the temp down to 60 for dry hopping for a period of 5 or so days, then cold crash at 40 to help drop the yeast out of suspension (Ales of course). You can keep the hops in while cold crashing, but I personally like to remove them because they can "catch" some yeast and other settlement on the way down. Its an extra step, and not necessarily a "have to" thing to do. All person preference and equipment capabilities. The longer the hops are in the tank, the more flavor to a certain point.
Spiny has a good method