It's a realistic 5 hours from what I understand. I was just in Avon and one guy came from Wilmington and he told me it was an honest 5 hours. Don't waste your time on the ferries -- it will save you around 27-30 miles total but will add about 2 - 2 1/2 hours...
We go a lot, leave early 4am catch 7:30 ferries to OC/Isle sleep on ferr. get to OC/isle at 9:am drive to next ferr. takes 5min then 45min to frisco you can be surfing by 11am then make sure your back for the 5pm ferr. home you'll be home by 11pm. ferr. saves gas and you can sleep. Check the forcast to know where to surf so you don't waste time lookn. Its worth it to go just for the day if its go'n off trust me..
Va beach, is in fact, much closer to OBX as is Raleigh for that matter since all NC roads lead to the capital. A lot military bases, marshes and wildlife separate Wilmington from Nags Head. I just took the ferry from Ocracoke. It takes 2.5 hours and the drive to the ferry is at least another 2.5 hours.
A few years ago I went up there from ILM with a friend of mine who had his pilots license. Trip only took us 30 or 40 min! Most beautiful flight I've EVER taken. Unfortunately my friend passed recently. I suggest tryin that out sometime.