Last winter EWR-BRS-EWR went down to five rotations per week in November, December, January and February (apparently only four per week were planned originally during this period).
It returned to daily in the first week in March. There were also some extra rotations in December giving six per week some weeks.
I don't know what is scheduled for the coming winter.
Why do you ask how long the CO service to EWR will last?