QUOTE(crookster @ Jun 4 2009, 01:15 AM)

and also what is the maximum piano time you should do a day, without doing an injury etc?
at the moment i am doing about 5-6 hours a day but again will change a bit when school happens again :/
and thank you again

There is no maximum time!
However, like Mad Tom said - practising too long in the wrong way is detrimental. For example, if you were practising 4 hours on the same part of 1 piece, after a certain point, it would not not help you, for various reasons. Its important that however long you practice, you make sure it is planned out so that you are not wasting time.
I also think it is better to play to an aim, rather than a timeframe. I'd suggest 4 hours is a good amount of time, 5 maybe if you can. The best way I believe to practice is as follows:
40 mins practise on scales, hanon, exercises, czerny etudes, something similar.
10 min break40 mins practise on a set out part of a piece that you find difficult/need to work on
10 mins break40 mins practise on a study or another pieces that is related to the difficult part of the piece you were just working on
10 mins break (or longer, as this is the mid-way point)40 mins practise on another part of the 1st piece that you were working on, preferably one that uses a similar technique to what you were just working on, or has similar demands.
10 mins break40 mins practise on a 2nd newer piece - to involve maybe "I'm going to learn the notes to the end of the 2nd page"
finishThe most important thing about this practice method is that when you get to the end of your allotted time for that particular subject/passage/study, whatever, whether you have perfected that bit or not - STOP. Set a timer and when it goes off, listen to it!
You're not allowed to keep going for 5 mins or go back to it when you should be on the next session. This way, you keep your practise varied and you get around to everything that you need to. Otherwise, you can fall into the trap (which I used to do often!) of playing the same piece for 3 hours at a time, 2 days in a row, just to try and get something perfect, which does not help! And it means that you are neglected the other, as important, parts of your practice.
Of course the breakdown is just a suggestion and it can be mixed up in a number of different ways. 40 min sessions is also based on what I prefer - my mind tends to wander after roughly that time. You might find that you need to do 20 or 30 mins, or you might find 45 mins works best for you. I would not recommend an hour at a time though, as after about 40-45 mins, your mind isn't learning as much any more (35 mins is apparently the optimal length of time to study!). You also don't have to only 40 mins. You could do 40 mins x 4, then 20 mins x 2 or something like that, depending on what it is tat you need to practise.
If you were doing 5 hours, again, you may need to have more breaks as it is a longer stretch. Another way to do it is 3 hours in the morning and 2 in the afternoon (what was recommended to me - I tend to have an hour/hour and a half break in the middle to have lunch and relax for a bit before starting again.)
Hope this helps!
C x