Any truth to the rumor that hops produce their maximum aroma when boiled for 7 minutes, and maximum hop flavor when boiled for 20 minutes? from chart on brewsupplies.com
I imagine that it differs from brewer to brewer based on their system. If a brewer can cool quickly, then perhaps they should add the flavor and aroma additions earlier, at the 20 minute and 5 minute mark, respectively. If they cool slowly, later may be better, perhaps at 10 minutes for maximum flavor and whirlpool for aroma.
That chart is useful to brewers to get an idea of how flavor, aroma, and bittering additions work, but I doubt the exact data points are correct for the large majority of brewers. The only way to see when you get the most flavor/aroma on your system is experience.
Man, I’ve been playing around with this for a LONG time. I wondered about the very same chart. I’ve been trying very late hop additions (after flameout, during whirlpool, etc), but feel as though I’m getting less hop aroma than the old 2 minute additions used to give me. I need to take better data regarding addtion time, cooling time, etc. so that I can move from having a hunch to knowing.
Me too! The more I brew the less I know. Here’s to killing more brain cells 
Thanks for the tip on cooling rates and their effect. Before I had discovered that chart, I had not ever read or heard anything about how flavor peaks at one point while aroma is more toward the end. All I had heard was “finishing”; what hops are recommended, and of course seeing lots of recipes, but no discussion toward why two separate finish points in the boil were important. I’ve discovered on my own that without finishing hops my beer has a poor “finish”. Now I’m trying to learn how to steer the finish in the direction I want by my choice of hop.
extremely well said. this is precisely one of the reasons why the same recipe in the hands of 3 different brewers will produce 3 close, but, different beers.