From Mr. Borneman
"Sarcophytons all shed a surface layer of dead waxy tissue from their surface. This is a regenerative action, and serves to rid the surface layers of algae and waste. Strong currents will help limit the frequency of this shedding. During such times, many people observe a sick looking and withdrawn Sarcophyton and assume that the coral is on its last leg, or that something is drastcially wrong in their tank. After the shed, however, the corals reexpand in full glory, usually larger and healthier than ever. "
In my reading the time frame for this to complete is completely dependent on the coral and the flow in the tank. If you can keep them in a higher flow tank the amount of times the will shed is drastically reduced because there is less detritus and algae accumulation.