The partitions are fixed in size... you can check the free space from Evo-X. I believe the games themselves handle cache management (turn off your xbox while playing a game and look in X, Y, or Z.... you'll see cached game files... start up another game and do the same thing and you'll see the previous game's cached files are gone) Likewise, your chances of running out of save game space on E is pretty unlikely unless you fill that drive with games and/or 'soundtracks'.
As for 'aiming' at me, dripgoss... I can't help it if you have a problem with the clarity of your writing.