That is interesting. I have seen Utopia Silver colloidal silver that is over a year old and still as fresh as the day it was made. The only thing that effects it seems to effect it is cold temperatures, which can cause clumping. I have about 4 gallons on hand that is over a month old now, and no difference with it either. I have been told that prolonged exposure to sunlight is a no-no also, though I have not tested that out personally.
I should point out that the colloidal silver made by Utopia Silver is made unlike any other I am aware of except Mesosilver. I doubt that anyone who has seen either home or commercial generators would recognize the setup they use.