You can check in bags as soon as the counter opens in the morning. I did this in HNL. See attached link.

http://www.flyertalk.com/forum/ameri...m-red-eye.html

If you are unsure, call the AA GLD/PLT/EXP desk and ask them to make a note in your PNR. If BOS operates different than rest of AA system and does not take the luggage, do post back and let us know.