Discussion - Methods to solve for skill progression time

Just looking for any general tips!

Say you want to control for how long it might take to reach max level of some character skill. There is too many variables to solve exactly, but we might at least be able to determine the absolute minimum required time if we did it like this:

Assuming you earn skill points by killing enemies…

Given a Minimum Minutes to Reach Max Skill, which assumes a rate of 1 kill per minute, then we can figure out what the MaxPoints per enemy type would be.

Then enemy types skill points value is 0-1. So we could solve to figure out how much time it takes to max a skill if you killed X amount of enemy type.

I think this is about as scientific as we can get with the time estimations (without using actual analytics to determine average kills per time period)? Curious if anybody else has some thoughts or different approaches to similar problems?