It depends on how long you want to leave the wraps in. If you leave them in any longer than a few weeks, the hair it self starts to slowly break away piece by piece. My daughter has had two, one lasted 6 months the other lasted 8 months before they eventually just fell out hair and all. I had one that lasted 9 months and then just one day fell out hair and all. If you only want them in a few weeks you can unwrap them, it just takes a lot of time and patience.
If you want to leave them in for an extended amount of time, I would highly recommend getting them done behind the ear towards the bottom. That way when the hair starts to grow back it is not noticeable. If you are going to unwrap them either way works. I have known a few people who had the ones done on the top of their heads at the part and let them fall out and when the hair grows back, it sticks straight up!