We had a first Gerrit cleanup day in September (T88531) which was mildly successful: We reduced the queue of patchsets without any review by 18% (25% for those submitted in last 3 months) and we learned a lot about (social and technical) aspects of Code Review.
It makes sense to iterate by repeating the Cleanup Day experiment in late February / early March 2016 incorporating T113378: Lessons learned from the first Gerrit Cleanup Day plus T101686: Goal: Define potential actions to reduce code review queues and waiting times/T78768: Agree on and implement actions to prioritize code review of patches submitted by volunteers.
We should also use this opportunity to improve awareness and knowledge about Differential's workflows across the developer community.
Related: T114311: [keyresult] Code review RFC (Differential) - Write, publish, publicize, and respond to/incorporate feedback./T119908: [RfC]: Migrate code review / management from Gerrit to Phabricator.