Multifactorial. Age, genetics, motivation, other life commitments, previous climbing and athletics history all play a part. But, in general, this method leads to steady improvement on a monthly basis in the elements you track. You might jump ahead or slip back, but the goal is steady, continuous improvement that you can sustain for decades.
Tracking with as much detail as you can sustain will help you discern the difference between normal day to day variability and actual trends.