Are you kidding me? 3-4 weeks is plenty. In ONE months time you can say with 100% certainty that is either does or does not have a URI, or mites and ideally if its been eating well you should have had more than one opperunity to examine its stool for texture and parasites. The only thing you may not know about is an airborn pathogen, and if youre using the same ventilation system throughout your house it MAY still get to your other snake regardless. Six months, thats an insane extreme. If you tell me you quarentine every one of your snakes that way Ill call you a liar.