This morning was exactly 15 minutes, but I voted 15-20 because I'll be adding in pre-shave as well as an aftershave in the very near future. I probably could have done it in slightly less time, but was trying out a different razor as well as blade.
Including cleanup (I get water all over the place and clean my razor after every use) 20 min weekdays, 30+ on weekends when I have the time to really enjoy a smooth, close shave with more passes.