IDG Answers is a community of experts who are passionate about technology. Ask a question or answer one below.
You may run into interface issues before the HDDs degrade to the point of being unusable. Still have a PC with an IDE interface, for example? That said there is a life span for HDDs, even sitting on the shelf. As far as I know, though, it is a known unknown. Think of VHS tapes. They degrade over time, but I have some pretty old VHS tapes that still play. I watched Pulp Fiction on VHS just the other day, and it looked fine (for VHS). I got it in 1995. Still, a HDD is magnetic storage. Magnetic dipoles have a half life, and over time data will be lost. How long? I'm not sure, but I have seen the figure 15 years used. I can't vouch for the accuracy of that figure, but that seems like a reasonably long time, and I wouldn't be surprised if the actual life is longer.