I think my experiment 2 ages ago saw arrond +30% for 100-120 professors, but was warrior which had +20% to military science that age.

You are definally better of nw wise going 2x novices over professors and keep resetting, but I'd pity the guy who needs to manually reset say 500 scientists once or twice a day as the age progresses, so don't go to much over the cap if that is not something that you want to do.