Wizzies tame lasts 2 hours (give or take a few mins) on most servers. But after they untame they revert to normal mob activity and can then be tamed again. Mir Revenge was like this, spend 45 mins to an hour taming 5 Venoctopus, level the pets then you get about an hour use out of them before they need to be re-tamed or killed.
If you do take pets out for everyone it gives wizards and taos back the edge they should have anyway.