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PREFACE: I would appreciate answers accompanied by facts and references. While I respect pure opinions, they don't seem to comply with the rigorous requirements of superuser.com forum.

How long is the service life of an SD card?

One often-cited number is "10 years" (for example here).

On the other hand, many manufacturers cite their products expectancy in hours, for example SanDisk® High Endurance microSD™ Card is listed as 20,000 hours (and this number is viewed as "high"). However, 20,000 hours equals to only 2 years and 3 month.

I know that longevity of flash memory can be limited by the following factors:

  1. Write cycles (irreversible damage);
  2. Charge leak (loss of data, but no damage);
  3. Hardware degradation (irreversible damage);

So, my question is - in an "occasional write" scenario, how long it would be reasonable to expect SD cards to work?

I have some flash drives, SD and CF cards that are older than 10 years, and they still seem to be good. Should I throw them out just as a precaution?

A question What's the life expectancy of an SD card? contains some useful information, but it is focused on the number of write cycles, and not so much on time in the absence of writes.

Also, consider the following scenario: An SD card is certified for 100,000 writes (just assume this is a fact for argument sake). Someone is writing to this card once a week. Should we expect this card to last for 1900 years?

P.S. I am puzzled to see why my question is viewed as "subjective". For comparison, life expectancy for U.S. in 2019 (for humans) was 78.87 years - and there's nothing subjective about this number. For water heaters, life expectancy is 8-12 years (a significant range, I admit, but still a numerical range). Why average flash memory characteristics are believed to be "subjective"?

Alexander
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    It really can’t be answered because it is subjective to quality as well as manufacturer. In general, I would never trust an SD card for long term storage even if it is just sitting around doing nothing. It is the lowest rung on the quality tree for flash memory devices. – Giacomo1968 Jan 08 '21 at 01:16
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    As Bob Newhart said about how long a plane can float: "Some go down in a minute or two. Others sink right away." – DrMoishe Pippik Jan 08 '21 at 03:31
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    @DrMoishe Pippik that's only because there is too little statistics on that :) And floating is not really a design requirement. On the other hand, aircraft lifespan is a well-established characteristic. – Alexander Jan 08 '21 at 17:33
  • "Subjective" is another way of saying that there's not "a good answer" to this question. SU is all about straight answers to straight questions, and this question has a lot of "it depends" that precludes giving a straight answer without a lot of discussion.. and this is a really poor medium for discussion. – Karu Jan 08 '21 at 18:57
  • @Karu I'd like to kindly ask you to help me identify the variables which produce "it depends" effect. For the manufacturer, I'm focusing on reputable ones (and I can reflect that in question). For the usage, I mentioned "light use" (and I can further clarify it in the question). While "heavy use" scenario is relatively well researched and I can google answers, "light use" longevity remains a mystery, which I am trying to investigate. – Alexander Jan 08 '21 at 19:20
  • For one, all of these things would need to be quantified, and that's a lot of questions. What is the threshold of "light use"? Is it based on read/write frequency or volume? How does that tie into wear leveling? Which manufacturer actually made the memory chips (not the one who's name is on the card)? What conditions are the cards stored in? What technology are the memory cells using? What is the failure mode upon which a card should be considered "no longer alive"? – Karu Jan 08 '21 at 19:37
  • From what I can tell the major reason of SD card failures is invisible physical damage. This applies especially, but not exclusively, to microSDs. Their fragility basically rules them out as a medium for reliable long-term storage. – gronostaj Jan 08 '21 at 19:43
  • @Karu I am perfectly fine if these were "ideal conditions" (as little read/write as possible, best chips, safe storage), but I was hoping there was some industry-wide statistics (or manufacturers claims). I can't believe that everyone is using flash memory with pure fatalism rather than facts- or theory-based guidance. – Alexander Jan 08 '21 at 19:47
  • @gronostaj Understood, thanks. The use case that I'm trying to solve is different from long term storage. I use my cards in cameras, and one week is the top time until I transfer the data to a more secure storage. However, many of my cards are old, and I am worrying whether the chance of failure for them is much greater than for the new cards. – Alexander Jan 08 '21 at 19:50
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    @Alexander That comment alone would probably make a good question. It's more focused than what you've asked here, tells us what's the practical problem behind your question, roughly what is the usage pattern and what kind of reliability is expected. – gronostaj Jan 08 '21 at 20:48
  • I'm just going to pitch in here as a somewhat high-rep user, and say that I agree with the comments. The question posed just isn't a good fit for the site, because it's not extremely specific and so it would be hard to find a single answer that is right (or specific and right in more cases than other answers). I recommend not trying to convince the whole community that this site should accommodate your desire, but rather, accept the polite advice and find another place to ask that question, or ask a different question. Challenging the system here for your question is unlikely to be fruitful – TOOGAM Jan 09 '21 at 00:16

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