One of the great things about Caesar dressing is the amount of SALT it
contains - from the anchovies, the cheese, the worcestershire (if you use
that)... this means that the dressing will keep a good two weeks if you
refrigerate it. This holds true for any egg-based dressing - I make my
own mayonnaise with a good hit of salt and it lasts at least three weeks
(I make a lot)!

Happy cooking,

lacticrat