My goodness -- forty hours a week? Even with ground school, etc., a CFI is
not going to give forty hours/week instruction under any circumstances.

You would have to be at the office 24/7 to get anywhere near that amount of
time.

Personally, I find the amount I instruct to be just about right. Enough to
keep me busy, but plenty of time to devote to business and other activities.
Instruction is only a retirement job for me, after all.