How do I set a maximum retention for history if I want it to clear entries older than 'x' days?

I see I can set a "keep history for at least __ days" setting, which might do what I want if when I also selected "clear history when I quit" *did* in fact keep the minimum history set in the area above, however it doesn't... in this case it clears all history. Why even have the keep history for at least __ days setting; it seems to do nothing at all. At any rate, what I want to do is set a *maximum* history to retain, be it 7 days, or 700.... then have the browser automatically clear anything older than 'x' either when I launch or exit the application. I don't see a way to do this, am I simply not using it correctly?