As a creator of tools which I hope will bring value to those who use them, user retention is a useful measure of whether user received value enough to return.
How would you figure that out without being intrusive? (That's mostly a rhetorical question to get me to think about how I would do it.) I'd rather use sats as an indicator. If people will pay for it, it's valuable. See my reply to one of Stella's notes.
Simplistically, if someone starts posting git events but then stops, then they havn't been retained.