I would tend to disagree with the thread you linked to. I think it take at least 2 weeks for you to truely be sure you have no diseases. I think if you do a search for "quarantine" you will find that most people recommend 2 to 4 weeks.
do 100% water changes in between fish.
some diseases like white spot, has more than one stage, if it has a stage where it leaves the host and free swims then it will be in the water for the next fish you put in there.