I think a tag can sit for ever. 72 hours is how long you have to post it. I just reread the rules. A 50 mile rule might keep the game from getting lame. And keep idiots like me from hoggin tags.
#7 The tag must be posted at least 50 miles from its previous location
It does have a nice ring to it. Who makes these changes? The person who started the game? What do you guys think?