321? Yes, this image explains why 321 is so important.
A client at Nestle called me and asked if I had an image that I had retouched for them over three years ago (Top, their original. Bottom, my version). Without even looking, the answer was yes! I knew I had it because all of my work is saved to three different places on two different kinds of media and one is kept off site. That's dpbestflo's advice and it helps me to keep my clients happy. In this digital age we need to take equal but different care to assure that our images are archival. 321 is the best way that I have found so far. Oh - for me 123 means 2 huge hard-drives and DVD's.