Yes, I agree that it may be necessary to change the media it is stored on from time to time, but the digital image is not going to degrade like a negative does.  As long as you do not let your storage device get old enough that it is outdated before you move the data to a modern one you will be fine indefinately. 

I may be wrong, but I'm thinking we have reached a point where current file types are not going to suddenly become obsolete.  There is too much information out there already to allow a lack of backwards compatibility in consumer areas.