How can i save individual render passes?

How can I save passes like shadow,reflections,AO, etc, in the blend or maybe some image so i can composite later, without having to re-render the whole damn thing?
Or do I HAVE to finish it in one sitting?:confused:

To save an individual pass or subset of passes or even just an intermediate comp, route the pass to a file output node. On each frame, an image file will be saved that contains the info. Use an exr file since some data (like Z) is outside the normal 0-1 range.

Alternatively, use a Multilayer formatas your output. This is a custom EXR format that saves render passes and the Z and the composite image all in one (big) file. When you load that back in later using the image node, all the saved sockets will be there as input.

Hi thanks. THe second suggestion works

but the first will need individual file outputnodes for every pass right?