The 230kts until retracted is a boeing recommendation and VNAV schedules 230 until all leading edge devices are retracted. It is done to cover a possible stuck flap situation and keep within the speed limitation for that case. During approach one is usually decelerating and therefore the airspeed is decreasing anyway. However even in that case boeing recommends to select the next flap setting only 10kts above the current flap limit speed, which for example means flaps 1 at speed up plus 10kts.