I know of another long term project using a 450D in Dubai.
There are some tips on doing long term time-lapse on our web site.
http://www.granitebaysoftware.com/TipErrors.aspx
Scroll down to the section titled "Avoiding Errors".
Be sure to use an uninterruptible power supply for the camera and computer.
Set the camera to manual focus.
Check frequently to make sure everything is ok.
Unload your data so the drive won't fill up with images.