This is new. Now that we no longer have to run site evaluations manually ourselves, we figured we would expand them to graduated sites.
Tim Stone hit the nail on the head in his comment:
Maintaining quality over time is just as important as starting off on the right foot.
Now, this is somewhat experimental. If these evaluations prove too distracting or not particularly helpful on graduated sites, we'll turn them off. In the meantime, the queue should pop up for a week every 90 days.
Update: after reviewing the results and responses across the network, we have disabled these evaluations for graduated sites. If specific communities want to do a periodic spot check of their own, we can fairly easily provide a random sample set of questions to them, but otherwise... y'all are "free and clear" once the beta period ends. :)