Well, there are other dependencies. A mass of solid is going to shield the inner mass from moisture. Even more so, as the mass coats itself with liquid. At some point, an equilibrium is reached between the concentrated solution surrounding the hygroscopic salt, and the ambient air.
That's why quantitative drying generally specifies a layer of substance no deeper than a millimeter. Even though that describes the reverse reaction, you see why its important.
So, you've got a controlled mass, in a thin layer that you've defined, you have it on the weigh pan of an analytical balance in a controlled humidity environment. Then you can plot the gain in weight as a function of time.
The question is why? If its not important enough for you to do, maybe its not important enough for anyone to do, and there's no table or reference to find the information. Or maybe you can find a table of values such as you're looking for.