Supporting your exponential hypothesis, I noticed after my 5 year break from piano that I could still play scales at pretty much exactly the same speed, and I s

Supporting your exponential hypothesis, I noticed after my 5 year break from piano that I could still play scales at pretty much exactly the same speed, and I still had a lot of the muscle memory. My teacher when I was in school had me doing them in 16th notes (semiquavers?) at 160-180 bpm before I stopped.