Alot of the Napa paint products are made by Sherwin-Williams.

I've not used any current Napa or SW products BUT

Best advice I could give is to search SW website or have the counter guys give you copies of the product sheets (P Sheets) for each product.

Also, many hardeners go "bad" after they have been opened.

There is usually a date on the can, if any doubt don't risk it!