Read interviews from top people working in the Art Department in the movie industry today. Production Designers. Art Directors. Storyboard Artists. Costume Designers.
It really does depend. On the whole, a large studio film in the UK could be 9/10 months work. The prep time is longer as is the shooting schedule. I have worked both in the UK, where I started and the US, where I now live. In the UK the Graphic Designer is really responsible for a large amount more work than the US. That may sound bizarre in terms of the work load varying but in the US there are a lot more print houses and production places that can facilitate some of the graphic design parts where as in the UK, the Graphic Designer creates all the Art department, set dec & prop pieces – no matter how big or small.