It depends on your own personal beekeeping management style, type of bees, and local conditions.
Every beekeeper develops his/her own methods. Some put a second brood box/super on, when the first is 70% occupied, moving a frame or two of brood into the center of the new super. In some locations doing this by the time they've reached 70% occupancy, may be too late to help reduce/eliminate swarming. Most all management with beekeeping is local and personal.
It also depends on the type of gear you are using; Top Bar hives, Langstroth, 10-frame deep, 8-frame deep; 10-frame medium, 8-frame medium, or combinations of the above, and etc.
There are so many management permutations that it is even difficult to remember them, in order to describe them all.