That highest speed is wonderful for keeping sheets from rolling up during drying. Without the three speeds, sheets can be kept from rolling up by drying them when the lint screen is full. What happens is that the sheets tend to get sucked against the exhaust grill and start to tangle. If the air stream force is reduced by a full lint screen, the sheets are not pulled against the grill and they have less propensity to tangle unless they are overdried in which case they will roll up anyway. The highest tumble speed holds the sheets against circumference of the drum and does not give them the chance to get pulled against the grill. I mostly just put one sheet in its own dryer, the pillow cases in with the flat sheet.