Not necessarily -- depending on the *paper* and storage conditions,
including the ambient temperature & humidity, coated paper can easily
keep a couple of days, and as much as 5 or 6 weeks. I haven't tested the
pH of papers, but I suspect that's a factor. The only way I know is to
try it. Best storage would be in a dry box (calcium chloride), but under
weight is good (keeps out the air).
Also, my suggestion would be that you need a benchmark for cyanotype --
starting right out with the cockamamie filter paper is kind of a barrier
to doping out the process, however esthetic the result is/will be. Why
not make a couple of test or work prints on a good rag-content typing
paper, or a neutral pH rag drawing paper to get the range and some kind
of criterion.....
Judy