Depending on where you are in NC, my BIL is a criminal defense atty and could help if you get caught speeding. ;-)
He actually gets stopped about twice a year, but usually it's close enough to home that the troopers and sheriffs deputies know him.
I drive in NC a fair amount and usually go about 10% over the limit. Never gotten a ticket in NC.
The difference in driving 90 and 78 for 180 miles (2 hours at 90) is 18 minutes. Actually, if you've just gotten off a plane from SOV, I'd suggest care and driving a bit more slowly than usual.