I guess, it is the traditional cyanotype formula.

I have once used 2 days old coated papers, they work. That does not mean they are ideal to use. But in a very humid areas, highlights of the print would be fogged after a day. (I have also seen a week old paper with fungi on it.)

IMO, stored paper will behave differently then fresh coated paper, for consistency it is wiser to coat and use with in few hours.