I recently played a course with a friend, who, on his home course ( a great one) was a real whizz on the greens. Virtually everything he putted was only ever short or long by a foot or so, and the direction, no matter how much break, was always spot on.
However, on unfamiliar territory, his directional radar was all over the place on a great many holes.
Obviously playing one course day in and day out for any length of time is going to affect your ability to read putts, but do really great greens defy the ability to easily guess their secrets, no matter how many times they are played?