It depends. I usually do 3 passes WTG, ATG and XTG with touchup to get BBS or just a shade below BBS. I have never timed it, but I would say approximately 15 min. Sometimes, if it is one day stubble, then I may just do 2 passes for a DFS depending on my mood. I have completed 28 traditional straight and 24 shavette shaves. I can't wait to hit 100 shaves for each razor.
Although an older thread I really appreciate hearing what others do. A member spoke of getting a blade so sharp they couldn't use pressure at all. During my first pass I am definitely using some pressure, not against the skin, put in the amount of force to cut the hair. While a sharper blade might cut more easily on straight strokes, around the corners and rounded areas the potential for blood loss could more easily occur. I'm presently experimenting shaving off a stone edge vs diamond or chromium oxide. There might be more resistance felt on the first pass, but after two passes and clean up the results are the same as with the paste.