If you are using a dryer for permanent press, it is a great waste of energy to use the low speed spin. Its original purpose was to reduce wrinkling of line dried clothes. The heat needed to relax the wrinkles in the fabrics is supplied by the dryer and it is sufficient to smooth out the wrinkles from the high speed spin. GE originally supplied an air restricter plate with a very small air opening that replaced the lint screen when wash 'n wear loads were dried on 120 volts to raise the dryer temperature, but when I was runing a WP dryer on 120 outside my first summer in this house, it dried permanent press items just fine. Once the load is dry, the temperatures will climb, even on 120 volt operation. Maytag's electronic auto dry did that when W'n W or Perma Press was selected. It continued heating until the air temperature reached 165F.
The low speed/shortened spin is great for all cotton fabrics that are then put into a hot dryer for about 5 minutes. The heat relaxes the wrinkles out of the cotton. Shirts, for example can be removed, one at at time from the dryer, and put on hangers. Their seams are stretched and panels pulled smooth. If fabric softener is used, no ironing is needed for casual wear and surprisingly easy steam ironing is needed for dress wear.