If the temporary directory, is where all your renders go.  I could imagine that would take up a lot of disk space.  Especially with animations.  My question is, do you have to delete these files.  Or does the program delete them at the and of the session?
This may sound like a dumb question, but I want to make sure.

Programs are supposed to clean up their temporary files when the program closes, but I'm not sure how well blender in particular does it.  If you have it set to the default system temporary directory, the operating system may also clean it up.  Personally, I've never had a problem with blender taking up too much space there, so I wouldn't worry about it too much.

Blender is not too good at the clean up, I often find lots of images and also bphys files (particle / physics calculations??) in there. It is in actual fact dead useful for those times when you have been a complete banana and accidentally deleted things....

Thank you, that's what I needed to know.

 I never even thought about that folder before,
Whenever I needed to render a animation, I change the location of that Temp file to where I want to save the animation and that's all that's saved. Same deal with the Fluid Temp Folder. I create a new folder for that certain fluid and direct the temp files there. Keeps me organized. ;)

 When I render a frame, I then go to File> "Save Rendered Image" . and save where I want. Looks like I'm going to have to go through the default temp folder now. lol No telling how much stuff is still there from the years. lol

 By The Way, I save my renders/animations/and fluid files on an external Hard Drive. I suggest doing the same.

I save my stuff to a mirrored raid....