I've left my carry on at T4 during a long layover about a year ago - bit of a nuisance that it's not in the same terminal as BA, but manageable, and certainly easier than taking the bag shopping
from the JFK website is the information below, which fits with my recollection.(
http://www.panynj.gov/faqs/airports....irportsJFKQu06)
Are there places at JFK airport to store baggage?
There are two places at JFK where baggage can be stored:
Terminal 1, Arrivals, 1st Floor near Alitalia & Olympic Airlines, open 7am to 11pm, (718) 751-2947
Terminal 4, Arrivals, 1st Floor, open 24 hours, (718) 751-4020
The cost for both locations is $4 to $16 per day, depending on size of luggage.