What I take from this is that Dustin Curtis plays Farmville and is a member of a shadowy group named "secret group".

Actually, the question of the piece is a good one. It's really about what you're optimizing for. As every halfway decent manager knows, you get what you measure. Which means deciding what to measure is one of the most important decisions you can make.

So, in this case, do you measure user engagement time for individual sessions? Or is there some sort of "engagement longevity" which might show a better timeline keeps people visiting more often over a longer period of time?

The other possible approach would be to see what could be done to make events and profile pages more appealing to spend time on. There may not be a way to do that if the timeline satisfies people, but it would be worth investigating.