How long will a hard drive, SSD or USB stick keep my files?

Manufacturers quote figures that describe populations rather than your drive, and none of them describe a drive left in a cupboard. The useful framing is that storage media are a rental, not a purchase: you get a number of years and then you must move the data on.

Safety

Step by step

1. Take mechanical drives at three to seven years in service.Failure rates are high in the first months, low through the middle years, and rise steadily after about four. Nothing about the drive tells you which year is yours, which is why the answer is backups rather than a longer-lasting drive.
2. Understand that SSD life is about writing, not time.Flash cells wear out as they are written. Modern drives are rated in terabytes written and the figure is far higher than a household will ever reach — a typical home user writes a small fraction of it in a decade. Wear is rarely what kills a home SSD; the controller failing is.
3. Know the cold-storage weakness of flash.Flash stores data as trapped charge, and charge leaks. An SSD or USB stick left unpowered slowly becomes less reliable, over a period usually measured in a few years and shortened considerably by heat. Powering it on occasionally lets the drive refresh cells. A USB stick in a drawer for a decade is not a safe bet.
4. Treat USB sticks and memory cards as the least reliable of all.Cheap controllers, no wear management on the low end, physical abuse, and easy loss. They are transfer media. Never let a stick be the only copy of anything.
5. Judge optical media by grade.Ordinary writable discs use organic dyes that degrade with light and heat, and cheap ones have failed within a few years. Archival-grade discs using a mineral recording layer are rated in decades and are one of the few genuinely long-life consumer options — if you can still find a drive to read them.
6. Plan for the reader as well as the medium.The commonest cause of an unreadable archive is not decay but obsolescence: nothing on hand reads the disc, the tape, the interface or the file format. Every format migration is a chance to re-copy, which is convenient, because you should be re-copying anyway.
7. Adopt a refresh cycle.Every three to five years, copy your archive onto new media, verify it opens, and retire the old copy. This one habit outperforms every choice of medium, because it defeats decay, obsolescence and silent corruption at the same time.
8. Keep two copies on different kinds of media.Two drives from the same batch can fail the same way at the same age. A drive plus a cloud copy, or a drive plus archival discs, are genuinely independent.

Alternatives

• Two external drives, rotated and refreshed: Cheapest practical archive for a household. Needs a diary reminder every few years to copy onto new drives, and one kept elsewhere.
• Cloud storage as the second copy: Removes the media-decay problem entirely and adds an offsite copy. Adds an ongoing cost and a dependence on an account remaining live and paid.
• Archival optical discs: Genuinely long-lived and immune to accidental deletion and ransomware. Limited capacity per disc, slow to write, and you must keep a working drive to read them.
• Prints and paper: Unfashionable and extremely effective for photographs and vital documents. Survives every technological change, needs no reader, and is the copy families actually still have after forty years.

Questions people ask