Put in as many markers as YOU feel YOU need- never mind anyone else's pet peeves. You'll find with experience you'll need less and less markers. I put them as close to the pavement as I can get which is usually 2 inches or so out. The snow will fall back that far anyway most of the time so I don't worry about it. Accept the fact you will break some markers every year (or your customers will) and put them where you need them. They're cheap enough to replace as needed versus hitting a wall, rock, pipe, or flower bed/grass and repairing the damage.
I've used 18-20 stakes in a drive before, some drives I have 1 stake. It depends on the drive. My drive I used to use 12 stakes (long u shape), but now that I've been doing it 4 years I'm down to 9-10