4 app programs were always the norm until the bean counters got involved.
A good 4 app program is great for most lawns and works very well.
That being said I "offer" up to a six app fert program with all the other bells and whistles too.
Creech got it right on a lot of points and slammed Efficiency pretty good but it's true. We do six apps because we can, not because we should.
When I started it was four apps and an optional late fall of high K product. Now it's six apps all high N.
I also know that 2lbs of N max was recommended for northern turf back in the day too. Not sure what they are up to now, and fall is all about heavy N.......
Buncha bullshit to be honest.