It is a slippery slope. If your thinking is just passive monitoring (as contrasted to goal setting), then it should have no impact on your performance. However if you use if for goal setting, as you get closer to “your mileage goal”, it could lead you to make a sub-optimal decisions regarding what you do on your bike OR feeling badly about such decisions that may be better for your performance.
Of course, you can do anything you choose and undoubtedly you’ll get some good suggestions in this post if that is the path you want to choose. I’m just trying to highlight the downside of setting goals around metrics that may be counterproductive.