We check the bag immediately and if it's excellent, then she gets to keep 3 and gets fed more.   If we feel she can only carry 2, we pull one immediately and either spike it on a single if we have one, or more often, it gets colostrum and into the bottle lamb pen.   It's harder on the lamb if they once bond to the ewe.   Most of our trips get one yanked, and if it happens right at birth, no crying from the lamb or the mother.