Interesting insight. So, for someone with a starter that hasn't activated after two weeks. What would you suggest to try to make the cells as active as possible? I have tried everything.
If you aren't seeing growth from activating a starter for two weeks, then I would say the cells are dead. I could put out just a plain water/flour mixture and capture a "wild" yeast in that timeframe. Was this starter in dried form when activated? Was it exposed to heat?
Regardless of how many cells you start with, the growth RATE is pretty much the same for all yeasts. That is a doubling of cells every 90 minutes or so. In the replenishing regime, if you start with less culture it will take them longer to achieve stationary phase. (I incorrectly called this "lag phase" in previous post, I corrected this.). If you start with more culture, they will reach stationary phase sooner. This has to do with the cell density. The stationary phase can be thought of as "maximum cell density". Once this point is reached, the cells undergo changes and slow their metabolic rate. The yeast know when they are becoming to dense for the media they are growing in. You can play with this saturation point and make the culture take longer to reach stationary phase by changing the ratio of your replenishing scheme. For example, instead of a 1:1 culture to flour ratio, use a 0.5:1 ratio. The downside to diluting the culture like this is it leaves it vulnerable to being contaminated or taken over by another organism, so that's why many prefer the 1:1 ratio. Remember, no matter how sterile you are, the flour, water and utensils are more likely to introduce something every time you replenish.
Using very little culture to activate (which is typical) or replenish is also not very good. There is a certain minimum number of "cells to volume" food source that needs to be established for the cells to reach log phase. A lot of time people activate a small amount of starter in like 2-4 cups of flour. This is almost so dilute that it's the same as just mixing flour and water then waiting for something to be captured. So until the culture is strong and established, the volumes and food source need to be kept very small.