MattNH is like me, we see the same questions being asked week after week and we have answered them all before.
We then see the same answers being given by the same people, time after time.
He's quite right, the information is on the site if you look for it.

Your short answer is; Its up to you.
Some people cut it right back to the hairline, others leave about an eighth of an inch.
Some people say that if you leave that much, it lasts longer and is less prone to fray.

Personally, I cut it right back to where it meets the hair.