The next planned revision at the bottom of my pages have these values (see below for explanation):
Immediately come to mind:
When you see a page with a last-modified date that is a year in the past, does that mean the content is now out of date? When the last-modified date is yesterday, does that mean the content is very new?
What is also needed is some sort of status indicating the speed at which the content of a page evolves.
As a first approximation of that concept I have added to my pages a "next planned revision" date. It can have these values:
A page that has not been modified in years but has a next planned revision of "never" still has relevant content, it's just that there is nothing new about it.