Last I checked, the only airside connection between terminals at JFK is between T2 and T4 via buses. That means taking AirTrain (landslide), and lots of time. I’d have to have at least two hours to kill before I’d go through all of that just to get into a lounge. Even then I’d probably not do it.
JFK is like Heathrow in how the vast size and distance between terminals is such that you’ll seldom want to venture away from your departure terminal.