Although it doesn’t happen a lot, eventually your software will crash. This time around I was working in Photoshop CS6, after a couple hours touching up an image I hit save. Probably because of an overload to my computer it crashed before the file finished saving. (I was rendering some video in Premiere, typing an email, and had about ten other apps open. Not the best idea when spending that much time in PS…) Regardless I re-opened photoshop after running around the house kicking and screaming and to my surprise it brought the file back in full form. Nothing was missing! Then I remembered when I installed the CS6 Beta I did some digging around the preferences and came across this little box. Automatically Save Recovery Information Every: 5 Min. 
I ticked it not really thinking about it. But how could it hurt? So very glad I did! All of this work would have been lost for good in the older version of Photoshop. I haven’t noticed any down time with the program because it is ticked either. Granted the information has to be stored somewhere, so clearing the caches after a long project is probably a good idea. Also make sure you have enough hard drive space to keep a large file active through the save.
Don’t put all of your faith in this little box though! Save yourself a lot of headache and Save Early & Save Often!
Keep Shooting!