Thanks guys this helps a lot.

And James I also heard MR VAI say that he practices his solos. I also read (Can't remember the magazine) an article where he said he sometimes transform a part of his solo into a warm up exercice. I taught that was a good idea since we all should warm up good before playing. Helps you with those tricky turns and twists.

Personaly, a took part of a caprice for violin to warm up. I do it very slow to warm up my fingers and gradually accelerate the tempo. Good for building speed too. I still can't play the entire caprice but I enjoy parts of it :)