I have my renewal interview scheduled for 6.30pm, at JFK T4. Is there usually a long wait, with a risk that a 6.30pm appointment will end up happening at 7.30pm? Or do they typically pretty much stick to the schedule?

I have to be at T7 around 8pm, so I was thinking that 1.5 hours is enough for the interview and to get myself over to the other terminal. But if the 6.30pm time slot is meaningless because of long wait times then I‘d rather reschedule.