When I bought my first DSLR in 2004 I was vaguely aware of this and bought an external hard drive and burned duplicate CDs of every job that I shot. I still have the CDs (the gold ones that were rated for 300 years) and eventually backed everything I had kept onto M discs that were rated at 1000 years. I also still have working CD,DVD and BluRay burner/players so I can still access the files. But for the last few years I have gone with multiple hard drives since I am getting close to retiring from commercial work and so far that has been sufficient. When I see that a hard drive is getting to 2/3-3/4 capacity and is more than 3 years old I migrate the files to a new drive before anything really terrible happens. I strongly doubt that anyone will be that concerned about anything I have in 50 years and I am certain that there will be new file formats, new connecting cables/protocols and generally incompatible devices unless someone actively migrates these files to new devices on a regular basis. I don't envy anybody in charge of maintaining a digital collection over the long term unless they have healthy budgets and competent people to make that happen.
