although not exactly this BOS flight, I once did YVR-HKG on similar timing (2am departure?). What I did was check-into Fairmont airport hotel around 2pm and wondered in Richmond but ate in hotel and just relaxed and napped. Then set my alarm 90min prior to departure and stroll down to check in.

I thought that was money well spent. It was end of our journey and wanted to take it easy instead of packing with activity for last minute.