I don't know. Have I just been lucky with hard drives? I was actually surprised to find out that people have had issues with their hard drives failing, especially ones made in 2000 and beyond, considering how well my own have held up. I guess my secret is, keep them dust-free? Clean them every once in a while? Don't handle the underside? Don't shake the drive or the computer it's in, and if you have to handle the drive, do so very carefully? The only bad one I've come across is a corrupted one I got from a friend. It was a Maxtor brand which, after checking around the Internet, seems to be a poor-quality brand.
Corrupted flash memory is already an issue with Wii and it hasn't even been five years yet, plus it is likely to be on around for longer than a five-year cycle. The scary thing about systems like the Wii is that, if the flash memory gets corrupted, the system is 100% unusable. I don't like that idea. If the next system has internal memory, it should be able to function after it goes, relying on the expandable memory, or it should otherwise be somehow replaceable.
What systems use batteries in the last decade? The last one I know to use a battery for saving is the Nintendo 64.