I think they need a clear place in mind to apparate to, so I don't think they can go to a place they've never been to.
As to how far they can go, I know it has been discussed on the board before as to how long a spell that didn't hit it's target will travel for. I think we came to eventually the magic would die out and burn itself out in a lengthly travel. I assume that this would be the same. More powerful wizerds can probably go farther then most, but I think it all depends on how much power you are useing when you do it.
http://www.keycasplace.tk
Keycas Place [12:33 AM]:
http://www.network54.com/Forum/thread?forumid=137625&messageid=1082583843&lp=1082689025 I LOVE HELEN!
ZigZag D7 [12:35 AM]: lmao.
~Link goes to specific thread.~
"Let's all play a game of hangman! Now who should we hang"? ~Riley
CPGKeyca = AIM
Keycas Place = AOL