The maximum on the poll is considered the minimum for most tanks.
My least stocked tank is a 125g with about 8-10" of fish. And it still see's atleast a 50% weekly. All other bigger tanks get weekly 75-80% changes.
I have several little tanks under 75g and since there so easy to do they get water changes 2-3 times weekly. But most of them have breeding fish and baby/juvie fish in them.
I dont even do once a week. Maybe around 4 times a month. I haven't ever had a heavily stocked tank before. That'll change come the spring time though.
I chose 40x/year as an estimate, but now that I have my automatic water change system set up I am doing 5% water changes 6x daily (2190x yearly if I multiplied right).