How long your yeast feed and reproduce after feeding has to do with a number of factors - what was the microbial count to start, temperature, amount of food introduced, hydration, etc. Once the food is exhausted, they will start to die off.
The activity of the starter will affect your fermentation time first and foremost. If you introduce more yeast (a more active culture), your fermentation will be faster. If you intoduce less, it will be slower. Assuming you take the dough fermentation to the same point (as opposed to fermenting for the same time), most of the finished dough attributes should be similar whether your culture is more or less active.
I think the most important consideration to worry about it having a similar level of activity each time you use the culture. This allows you to forecast your fermentation time and aids in consistency.