Yeah, 4-5' up the backboard is a good fast serve, at least 110 in flats, easily 90 with topspin, just a solid 4.5 level serve.
But temperatures do play a factor. In 80 degree heat, that serve is very good.
But in 55 degree cool, that kind of serve is superlative.
I seldom get that 5' bounce anymore on flats, but then again, I seldom play in temps over 70.
Today is 46 and I'm headed out to play.
Back when I was playing at GoldenGatePark, in 65 degree weather, my first flats usually bounced over the back railing at courts 1-4. That rail is 5' high, but then again, I was 30 years younger.