Showering isn't exclusively shave-prep. I'm doing it anyway. However, I would rarely have a shave without showering first. It gets the beard well-hydrated. Without that starting point everything else is less effective. Of course, as with almost everything else in life, do whatever works for you. My shave time now is about 10 mins; when I first started using a DE a few years ago it was closer to 40! Don't ask me what I was doing because I couldn't tell you.