How long to clear custom and collect baggage in JFK

How long to clear custom and collect baggage in JFK?
I will be traveling to JFK from Singapore on a Travel Visa Pass then will have to make a transit from Terminal 4 International to Domestic Terminal 6 for JetBlue flight to Buffalo, NY. I'm wondering how long I will have to queue to clear international customs, collect my baggage and run over to clear security and check-in to my flight to Buffalo, NY. I'm thinking of 4 hours in between arrival and departure, is that sufficient? Also I will be booking my domestic from JFK to Buffalo via on-line purchase. What if I miss my flight? It's non-refundable, what happens then?
Air Travel - 2 Answers
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1 :
it is depend on your baggage , if hand carry no time taking within few minutes you will be clear,
2 :
The amount of time needed depends on how many other flights arrive at the same time and how many Customs officers are on duty. There is no way to predict it. Based on my past experience changing planes at JFK, four hours should be more than enough time unless your arriving flight is very late. Jet Blue is not responsible if you miss your connecting flight. However, they will probably accommodate you on a later flight. They're not responsible for paying for meals or hotels if you have to wait a long time for another flight or if you have to stay overnight.