If I'm using a safety razor it's very easy to stop at a 3 pass shave, which doesn't quite get me to a perfect shave. Sometimes I shave with, then against the grain only, for a much better than average shave. Maybe I'm too pernickety, but getting truly-and-utterly-homogenous-never-grown-a-beard-in-your-life-smooth is very difficult. There's always some sensation of hair somewhere from some angle, despite the fact that it's invisible. Sometimes it takes me a long time to find it, passing a hand over my face for a full minute to feel THAT tiny little inconsistency in the hollow between my jawbone and chin or wherever, but I always find it. I've had truly BBS only a few times, despite being 95% there more than half my shaves of the last 45 months or so. I found a 37c was one of the worst razors for this. Great first pass then downhill from there. I don't worry about it and I step down the next morning at the merest hint of irritation.