I had to drive back from Ames IA to Minneapolis MN (200+ miles) right after picking it up with 8-9 miles on it. The salesperson suggested varying speeds a bit, stopping a couple of times and avoiding sudden starts and stops. Basically the same as the manual. I ran from 60 to 70 MPH on the way home (speed limit 70) and luckily didn't have to make any sudden stops! We drove up to Duluth and back this weekend and put another 300-400 miles on it; same routine.
It used to be with older engines that you didn't want to "score" the cylinder wear top and bottom points by staying at a constant speed; so you varied the speed. Also you wanted to change the oil early to remove any metal filings. But not so much today with newer precision machined engines.
I had to apply the brakes today while traveling around 15mph to avoid an accident. Mileage is under 200 and I felt sick inside after doing so. I hope/am sure there's no harm or significant reduction of brake life expectancy, however.