I am a hardware engineer with 32 years behind me + hobby since I was 10 years old
Hardware is not software. Hardware is made from materials. Materials change over time. Two pieces of hardware are not identical. One can fail after a month. One can fail after 10 years even if the official mean time between failure is 3 years.
If an electronic component has failed at warm temperature replace it! Temperature accelerates transformation of materials. When you do accelerated life tests the two main components in the test is hot soak while running and extreme temperature changes. A component that has run too warm has been aged in an accelerated way. Replace it while you can still get data off it
As many say SD cards are not really designed for heavy reading and writing of small amounts of data.
Both SD cards and SSDs are made from flash memory. Flash bits can be set to 0 individually but cannot be reset back to 1 other than erasing entire blocks.
So when people talk about how many petabytes you can write, then it depends on how you write. In a video camera you create gigabyte large files but you create them block by block in a stream where you add new blocks to the file. SD cards and SSD handle this very well.
But when you have software that writes few bytes to same few files over and over again the number of bytes that actually gets altered on the flash can be much larger.
And if you have an 8GB card already filled with 3-4 GB data of which a lot is dynamic data like the database then you ask for trouble.
An SSD has better wear levelling algos, it caches more data in RAM to limit writes, it is generally larger than an SD card so it has much more space to do wear levelling.
A spinning harddrive does not have a practical limit to how often you can change the magnets on the platter. But it has moving parts. The disks are spinning between 5000 and 10000 times per minute 24/7 which wears motor and bearings. Worn out bearings create noise and heat. The heads are moving. And over time material in general transforms. My rule of thumb is that when a rotating hard drive is 3 years old you should replace it if it has run 24/7.
SSDs have silicon chips that will eventually fail. It has voltage regulators that fail. Capacitors fail. It all fails. The cooler it runs (within limits) the longer it lasts.
I absolutely choose SSD over HDD in my Home Assistant machine.
But even with SSD I ensure that
- my SSD is much larger than the data stored on it
- not leaving large unused gigabit files from forgotten VMs or containers from experiments
- limit the recorder function in Home Assistant to the absolute minimum. Why record data I never look at just because I can?
- limit logging to what is needed. If you enable debug logging, remember to disable it again.
- if the SSD is an M.2 type buy a cheap heatsink for it. They cost a few dollars on eBay. They are easy to mount with a cooling pad and an elastic band that comes with the heatsink.
And again, if a disk SD card, SSD, or HDD fails because of heat, replace it!