If you put 365 for the max age. It'll look at all threads started in the past year and order them based on number of replies (or number of views or a combo of the two) divided by the number of hours elapsed from the thread start date until the current time).
I didn't say this was exactly what you wanted. I feel like what you want is to use the most recent reply time rather than the thread start date but one of your posts seemed to contradict that but I may have misunderstood it.
I never meant to imply that this feature was what you were referring to, I was just trying to explain to you what it does since you didn't seem to notice it.