Hi there!

The amount of time you *have* to spend practicing varies a lot from person to person. Apart from obvious reasons, like variations in the rate at which your brain can pick up and memorize things, it depends on where you want to go and how good you actually are in monitoring yourself.

For example:
You have two persons. Both start from the same level and have the same amount of "talent". One practices 2 hours a day the other 5 hours a day. Yet the one with 2 hours a day makes faster progress than the one with 5 hours a day.

How can this be?

The one with only 2 hours of practice might have a better practicing quality.
Like for example he plays a certain song and notices that he has a hard time learning it. He looks at what he does and concludes that his finger-movements are to un-economic. So he starts working on that specific matter and develops his own exercises. The other person just thinks "man this is a hard song" and keeps on playing it for hours without knowing why he has such a hard time playing it and what to focus on.

So basically what you need is a certain amount of knowledge concerning what exactly is vital for a good, flawless technique. Granted, this is something most people have no idea of when starting out.
So what you need is someone who points those things out to you until you are knowledgeable enough to develop your own training methods and awareness of your playing.

This site, for example, can be very helpful in giving you hints and pointers to that problem. Additionally - as i always say - nothing can replace a good teacher that is sitting in front of you, monitoring your work.

This might sound strange but everyone has a different amount of body-awareness. That means while one person knows exactly where every part of his body is and what it does at any given moment, others do not. That is not necessarily a disability problem like limited fine-motoric abilities. A certain amount of variation is natural.
So especially to those who have less body awareness, a person that sits face to face telling them what is happening is very important because the have a harder time translating the stuff that they read somewhere into appropriate movements.

Some of my students, that I have been teaching over the internet, had exactly that problem.
For example i told them to keep the finger movement very low. They tried and reduced their movement but they where absolutely unaware that it was still too much movement - they thought its ok already. It was not until i sat in front of them that they got what i was telling them.
This has nothing to do with stupidity or talent btw.

Azrael