I've searched the websites, but didn't find anything about JAC Viewer. Therefore, I can't provide the details required for the library update process and how long it takes. Kindly study its built-in Help section to see exactly how to update and how much it takes for this procedure.
Secondly, the developer's website appears to be available as well. I recommend checking their website where you can find contact details as well. Use that email address to send them an email for this inquiry.