This is really great! I've been wondering for a while how many of my followers have gone inactive, and now I know. Using the default options, only 26% of my followers are inactive lumps of driftwood, which seems encouragingly low.

However, I don't really care so much about a follower's posting history (unless I follow them back). What matters more is how often they vote. So I switched the toggle to "vote" instead of "post" and the percentage went down to 21% dead. Even better!

I think you should have weeks on the time scale too, in addition to months. I'd be curious to see how many numbers change when it's just the last week or two.