How long do you expect digital files to last?

In going back through my notes of the Mid-Atlantic Regional Archives Conference (MARAC), I see that one speaker talked about defining up front the lifespan of your digital materials you are creating. This is a point that we don't always consider. We may not creating digital assets that need to last forever. Perhaps the assets only need to last seven years for legal reasons, or some other defined length of time. So when thinking about a digitization project, think about the length of time you want the digital assets to last, then put the processes in place to ensure that they last that long AND (if necessary) destroy them at the appropriate time.