We don't have to be stingy with disk space nowadays. I save everything (well, almost everything) and I append date & time strings to file names for version history. One time I didn't save, although I wanted to, was when I was programming a mobile, and wearing pants with a fair amount of synthetic fiber, which especially in our dry climate equals static zaps. At one point I stuck the mouse in my pocket and it lost it (but later recovered); I had finished modifying the program in the radio but couldn't save it since the laptop was going wacko. Which I discovered when I went back inside and tried to save. But the radio was OK; I just had to read it back out the next time the guy was around. This is when I switched to a cordless mouse.
;B