[Humabout]

A four hour daily practice session is ehat the University of Miami School of Music's jazz program teaches. You spend one hour on scales, arpeggios, and technical exercises, an hour working on music pieces, an hour on improv, and an hour noodling and generally being creative.

So, 1d hours averaging 3.5 hours, doesn't sound the least bit unusual. It's worth noting that there is a huge difference between knowing notes and playing them well. A lot of work done to learn a song is about phrasing and giving depth to the music.

Another thing is that a really good musician must practice a lot to maintain his chops or theres a sharp decline in skill. So again, 4 hours a day doesnt sound unreasonable.

Lastly, one nit to pick: the only "complex" musical piece mentioned in the above post was Rhapsody in Blue.