Once every eon I get tired of my brush and do some optimization. It's probably only noticeable in the full sized image/when zoomed in. I used the brush on the left for years until I suddenly wanted a rougher looking brush. Did some optimization (middle) on my current brush but still wasn't happy and played around more with the settings (right).
I just really like seeing comparisons like these. And I find it interesting how the vibe can change with a different brush.