but there seems to be no pattern to the two lengths.
The pattern is that thicker disks take longer to take in salt. a 125g 4"-4.25" takes proportionally less time because rate of uptake and ionic diffusion is not linear.
Err slightly on the high side, you can't really overbrine, as salt take up reduces with time.
IMHO, this is only one side of the story. It is possible to overbrine, especially with 18-22% brine. Higher fat content, higher moisture all can lead to fast salt uptake, so that any decreases with time will be so marginal as not compensate for higher initial uptake rate.
What is the benefit of brining it instead of dry salting?
More even pH and salt gradients, also better control of surface moisture. With salt, you draw out the moisture, it dissolves, then penetrates the cheese. The salt and pH gradients are often not too even at the surface. This is partly why salt size and dissolution rate are so important. With brining, you're done when you take them out... dry up the surface to encourage PC bloom and off they go.
