FYI
BOS UC (RCC) agents have advised that as of 4/1 the boarding times will be adjusted. Boarding passes will be revised to reflect this change.
753's, 752's, and 739's and above will be 45 minutes
738's, 73G's, 735's, A320's, and A319's will be 30 minutes
Until 4/1, the policy at BOS is to board all narrow-body mainline flights at 30 minutes.
IMHO: 45 min to board a 752 or 739 is totally excessive. 753, I can understand needing 45 minutes.