How did he do it

[Franz_Liszt]

 How did Franz Liszt practice 8-14 hours a day without burning out mentally and physically?I am aware of the fact that he was a master of relaxation, but my endurance, mentally and physically, is high for my age. If I practice 6.5 hours ( 6 hours and 30 minutes for the dimwits in here) I get tired ( physically...anyway). How can you build physical endurance also? I know that my mind can last at least double what my body can.

[rachfan]

Franz, time is not the governing factor in practice.  Rather, it is a matter of focus, concentration, keen listening, accuracy, working out fingerings, taking in details of the score, and the ability to shift from "mechanical" practice to overcome technical problems and then to transition to musical practice in polishing.  Many people can accomplish in two hours of careful, intelligent practice what it may take others hours to accomplish with their ineffective practice.  So in practice, quality has it all over quantity.  Liszt practiced as long as he did because he was the first piano virtuoso, had a demanding tour schedule, and needed to protect and enhance his public reputation as the counterpart to the violinist virtuoso Paganini.  Given the repertoire he was performing, the hours of practice were probably justified.  You are not facing the same issues and pressures at the moment.  So your focus (preparing for your next lesson) can be done in far less time with attentive, high quality, efficient practice.

[Hmoll]

Dimwits?  well, I guess you're trying to endear yourself with the other folks in this forum.
The short answer is, I suspect there is a difference between the mental capacity that Liszt possessed and yours - although I don't know for sure because I don't know you, but I'm probably right.
The longer answer is I agree with what Rachfan said. Quality over quantity. If you are tiring physically before you are mentally, you are probably not concentrating enough. Try practicing less hours, and focusing more. Also, you need to take breaks.
By the way, although Rachfan makes a lot of sense, I will disagree that Liszt was the first piano virtuoso. He certainly was the first superstar pianist of the same ilk as Pagannini, but the Mozarts, Clementis and Beethovens might want to be considered virtuosos.

[Franz_Liszt_X]

What repertoire was liszt performing?

[88keys]

Well... Liszt, obviously!

Anything else he might have played is really not very relevant, because Liszt himself wrote some of the most challenging pieces ever written for piano.

I suppose later composers have written pieces of higher difficulty (Rachmaninoff, Godowsky), but Liszt obviously couldn't have played them...

[eddie92099]

Claudio Arrau also practised for sometimes 18 hours a day! There is a fascinating book called Conversations with Arrau where he talks about this,
Ed