30 minutes isn't necessarily a good rule of thumb. The hit should dictate the wait, it's so important to know where you hit an animal.
Here is some excellent reading from everyone.
http://forum.hunting.net/bbs/topic.a...00&FORUM_ID=19
<font color=blue>Good Luck and Good Shooting</font id=blue>
<font color=red>
Rob</font id=red>