*Disclaimer - I am not the original creator of the script, all credit goes to Aiffe on Tumblr*
I'm pretty sure a lot of people get the biggest peeves when SAI crashes on them and then loosing all progress when you've forgotten to save, well look no further the answer is here.
The script itself is easy enough, it's just an .exe file that must be ran after SAI has been opened. The autosave saves progress after every minute only when SAI is in focus on the screen. (e.g I'm using SAI then I look at something on Google chrome for ten minutes. SAI will not save during those 10 minutes and will begin to autosave again when I look back at SAI.)
After you quit SAI the autosave script will still run for a minute before quitting itself so if you re-open SAI you will need to re-run the script as well.
Download the autosave.exe here - https://drive.google.com/file/d/0B0kTdcq1nk1kU20tbWx1UWhCeW8/view?usp=sha