Advice on script length please!

I am developing a cms with multiple zones and user management etc.... My file is currently 1200 lines long and consist of 450 lines of case statements and then the rest are functions. I'm getting parse times from 0.2 to 0.8 seconds for the different pages depending on complexity. The script is due to be at least 2200 lines when complete and I wanted to know, is it worth splitting any of the functions into includes which are only called if needed, say if an admin is in user management, call the user functions etc... If I did this, would it make a huge amount of difference? Thanks ;o)