I save as I go, constantly for this reason.
I think an auto save is a horrible idea for the following reason.
Wwhat if you spent an hour and a half creating something that you decided you didn't like before the program crashed? It will ruin your existing file.
I've foolishly left reason open, and came home to edits made by my cats who walk across my 4 seperate midi controllers. Do I want that auto saved? Nope.
Maybe if the autosave wrote to a temp file, it would be fine, but then again i'll have 3-5 instances of Reason open at once, and even across multiple computers...
I can always recreate my sounds. I plot it all out in my head before hand so I know what I am aiming for, though if you dont know what youre doing and youre just turning and sliding knobs till it sounds cool, sure... autosave would be great for you. lol