I no longer believe that checking in at 23:59 is the best approach. In my experience of flying DCA-DTW almost weekly this fall, there is definitely a "new" sweep that occurs sometime in the early morning the day of depature. My new recommendation is to not check in the day before unless you see R availability in KVS or similar. Should you not score an upgrade at that time, cancel out of OLCI and hope you are automatically upgraded in the early morning.

It appears to me that NW is holding back more F inventory and dumping it into R and sweeping people into it the morning of the flight.