Safe is a multifaceted term. Essentially these storage media (I'm more experienced with solid state but HDDs may be included) the probability the data you wrote is the data you read is a function of how many program/erase cycles, how long ago that was, and naturally the part's specifics. For example, a lot of NOR flash is rated to 10 years at up to 100k cycles. But devices > 10 years old rarely make the news for their flash being dead. On the other hand, I believe there was a Tesla fiasco where their logs were wearing out the flash prematurely.
There's usually trends to look for in regards to that third factor. The lower the # of bits per cell, the higher probability the voltage level is still working the right range. Which is why so much flash is still SLC or pSLC capable. Usually this is more industrial. Then you have entirely different technologies altogether. NVRAM/FRAM/MRAM are various terms for extremely high (or infinite) read/write technologies while still being non-volatile (keeps its data with power off). I don't know how much of a drop in replacement those are. I think LTT had one of those on a flash drive a while back https://youtu.be/oJ5fFph0AEM, but it's so low capacity it'll probably be useless.
It may be possible to hack something up with a MR5A16A. It's a whole 4 MB but has unlimited endurance and over 20 years of endurance. It looks like it has more of an SRAM interface than NAND, but should be capable of saturating a USB high speed link. The drive would likely cost $75? TBH if there was a market it may be a fun project.
If you sacrifice some endurance you can go up to 1Gb per device which might be interesting. But the cost scales.
> But devices > 10 years old rarely make the news for their flash being dead.
Accelerated stability testing is fraught with potential issues, and any output is intentionally conservative.
An issue with estimating lifespan on new products is that they'll expose them to more extreme conditions, but those more extreme conditions may trigger (exponentially faster) higher order reactions that are relative non-issues at regular conditions.
Then you have things like activation energy requirements for a reaction that just might not be met at regular conditions, but happen at higher temperatures.
And an IC is quite the soup of molecules in varying combinations unlike a straightforward solution.
Samsung still screwed up with the planar TLC flash used in the infamous 840 EVO SSD, which had a real-world retention measured in months. Their "fix" was to issue a firmware update that continuously rewrites data in the background, but of course this has no effect if the drive isn't always powered.
There's usually trends to look for in regards to that third factor. The lower the # of bits per cell, the higher probability the voltage level is still working the right range. Which is why so much flash is still SLC or pSLC capable. Usually this is more industrial. Then you have entirely different technologies altogether. NVRAM/FRAM/MRAM are various terms for extremely high (or infinite) read/write technologies while still being non-volatile (keeps its data with power off). I don't know how much of a drop in replacement those are. I think LTT had one of those on a flash drive a while back https://youtu.be/oJ5fFph0AEM, but it's so low capacity it'll probably be useless.
It may be possible to hack something up with a MR5A16A. It's a whole 4 MB but has unlimited endurance and over 20 years of endurance. It looks like it has more of an SRAM interface than NAND, but should be capable of saturating a USB high speed link. The drive would likely cost $75? TBH if there was a market it may be a fun project.
If you sacrifice some endurance you can go up to 1Gb per device which might be interesting. But the cost scales.