Compositor : export output node when we want ? is there a way to save output file , after the "F12" render is done 

for example , i created an output node for my passes ,and the way it work is that the passes are automatically saved when the "F12" directly after render is done , no way for me to control when it happend , the only way ai can export thoses files to my desktop is by doing the render ...

what if ive done a 5hours render and forgot to plug in the compositor "use nodes" , the only way to get my passes back is to redo an entire render ? really ? can we choose to export when we want our output ? how ? 

thanks
Yes, if it was just a still render image, you can save each passes as a single image:



Just select the render pass, then go to Image > Save Image as

But if you want to render an entire animation without having to "Use Nodes" or even if you want to save the still render image passes as a single image file, you can save the render as an OpenEXR Multilayer file, but consider that the image file size could increase a lot.