It's only recently this has started happening for me, maybe the last month or so. The last update i installed was T3DPro SP3, and then reinstalled all the addons, Traffic, Color, KJFK, and KJFK Color.
I can say for sure, with the same traffic and colour set up this was not an issue when I first purchased JFK, I would play 3-4 hours no problems. Now I cant get though an hour and I have everything set to minimum in the settings panel to try help.
On a side note, I have a Cargo gate at the 13R end of the airport that aircraft wont pushback from, they will accept the instruction but wont move, I guess if it's like T2011 set up possibly a taxiway joining knot is missing?
And on the North side of T2 (south side of T1), aircraft will push back fine, then after accepting taxi instructions will do 2-3 pushback/loops before they find the exit taxiway, funny to watch but when sequencing can slow the flow down waiting for the pilot to find his bearings.
Still enjoying LAX though, no complaints there!