How would you store it once its open?

I always thought as it was soo full of crap, it dont go off, so dont have to refrigerate it, or eat it that quick

Well just AFTER using some that was opened a few months ago and kept in a cupboard i read on the side, keep refrigerated at all times and use within 4weeks of opening

So is that just a precaution or am i lucky not to have poisoned myself by now from eating tainted Mayo