I avoid the problem by dryhopping in the keg using a knee high nylon stocking full of hops. I drop in a stainless fitting for some weight along with the hops. I tie it off with some dental floss and suspend it in the keg so the hops are only about halfway down the keg. This way, dry hopping stops automatically after you drink the first half of the keg and you don't have to worry about taking it out until the keg is dead. The keg lid will seal just fine over the dental floss with no leaks. You might want to avoid the flavored floss. Same goes for used stockings unless you want the beer to taste like the hooker you swiped them from.
BN Army // 13th Mountain Division 