Long term parking at Kennedy is excellent.

The lots are huge, clean and safe. I have used them at all times of the day (including the middle of the night getting off of red eye flights).

As Jersey Guy said, give yourself an extra 15-20 minutes and save yourself some dollars.

BTW, in the long term lot, while it is $15 a day, they charge you in eight hour increments ($5 per eight hours) so you are not hit with a full day charge unless you are there over sixteen hours of that twenty four hour period.