You're not the only one. I too have found the few times that I take CX888 with an on-time arrival at YVR that they can't seem to get the aircraft turned around and off to JFK promptly.

It always is a dissapointment after the normally fine CX service.

Likewise when I take CX889 back to HKG it usually leaves JFK late since YVR couldn't turn it around ontime and JFK can't seem to cut down their turn time and instead taking the whole alloted time.

I recall a few times sitting in the BA lounge at JFK barely able to keep my eyes open as the YVR-JFK-YVR sector was delayed. Of course this was when the flight still left around 1130pm.