If you know the general size of your media, then it is much less of a headache to you and whoever else uses the system if you partition.
Heres my drive setup at work:
E: Project 1 - 18gb
F: Project 2 - 40gb
G: Project 3 - 40gb
H: Project 4 - 60gb
I: Project 5 - 60gb
J: Project 6 - 120gb
This is a very expensive editor using several SCSI RAID drives, but it's the same basic idea. For those really long projects, we just go over to the next unused partition.