Theres always the Aspire Lounge in T5 which is ok and certainly can make for a relaxing experience before a Y flight if you don't have status but theres a few places to hang out.

A walk to the galley well after dinner and sometimes striking up a conversation with the CC asking for a cuppa can in my many Y experiences kill 20-30 minutes and most in my experience like this but you have to time/judge it right and probably more applicable on much longer sectors.

IFE should be OK on the JFK route generally but have a back up. Book, IFE, magazines. If your in a 747 it's worth going for a window ar the rear. 51/52 specifically sitting in the K side going west so the sun isn't blazing in. Watching the sky/clouds, thinking can kill some time too!

So board, enjoy the take off, watch a film, eat, little nap if you can, stretch out/walk, play a quiz, read and before you know it there'll only be a few hours until touchdown