Sky Priority check in is open from 0430 to 2030 (closes earlier on Saturday). But someone is usually there until about 2100 on all days except for Saturdays.

Also, bag drop cut off is 30 minutes to departure regardless of destination. (Except LGA which is 15 minutes)

I would leave enough time because as I have said in the past the 30 minute deadline is firm especially for international as handwritten tags are frowned upon and will be done only in the most extreme of emergencies.