I had an attack once (was enough) and I was in the ER for about 12 hours. As I recall the pain was super intense for 6 hours more or less. Hard to exactly remember cause of the morphine and they kept me for a while.
I'd imagine that everyone is different because I've heard of some who have the pain for days.
I hope you're not having one-it really hurts-a true 10-changed my perception of the 'pain chart'