Don't think of it as speeding up the process, just consider that it helps insure the fermentation finishes out well. Where fruitiness is concerned, the slower the fermentation the better. However, it will certain help when you are not doing a cold temperature fermentation.
Put it on to get fermentation going. When it gets really going (generating its own heat), turn it off. When fermentation slows again, turn it back on until the wine is completely dry. It will help finish out the wine to completely dry.