Sorbate is just like the oxygen sterilizers, it works immediately on contact. The problem with the quantity of sorbate that the kit makers give you is that to many people it raises the sorbate level enough to be detectable. Some people can really detect it in the taste. If I'm making a 3 gal batch, I always use only half the packet. The whole packet does alter the taste.
Even if they save money by not having to make a separate packet with only half as much in it, they should put in their directions for ports to only use half of it.
Didn't think that I could taste the sorbate until I bench tested......with the whole packet, there really was a difference.
Sorry, but I've been layed up after a heart attack for a while.....everything fine now (guess I just didn't drink enough red to prevent it -grin).
Noticed questions a while ago about how much brandy to use to fortify. The easiest and most accurate method is to use a Pierson Square with it's simple calculations. Should be easy to google and find out what it is and how to use it. You know that alcohol % of the wine, and the brandy.....so it's very easy to do the grammar school calculations.