I'm not sure what you mean about linear behavior...
Imagine you do 100 ped hunts with the same weapon on the same mob, and plot your prof level against the number of hunts.
You will get a curve that looks like y = k*log(x)+b, where x is your hunt number and y your current prof level.
In reality it's not log(), I don't know what it is and ofc it'll have some random noise added to it, it just an example
What I'm asking is how it behaves at infinity.
So you are saying it becomes a straight line and grows linearly after you maxed 10k skill point relative to the profession?