What is the expected durability of a Mac mini (2020) flash storage?
Solution 1:
I've had my 2018 Mac mini with 512 GB since November 2018 (around 580 days). According to DriveDx, the on-board SSD has been powered on for 28 days, despite the fact that the Mac has been switched on almost permanently.
The drive has written a total of 17,1 TB of data, according to the SMART data from DriveDx. I've heard 300-600 TBW bandied about as a typical SSD lifespan. (300 for the blade on a 2014 MBP; 600 for a 2018 Samsung EVO NVMe.) In which case, I've used about 0.06% - 0.03% of the drive's writes.
So it should last me 26-52 years. You may be able to extrapolate a result based on your own usage.
If you are expecting to write 8 times the disk's size every month, then using a larger external drive, which can be replaced more cheaply if necessary, may be a safer/better option.
Solution 2:
As mentioned in the other answers, Apple does not give those specifications in their documentation or on their web site.
You can get some kind of estimate by installing the program smartctl from smartmontools, which can query your specific drive for its health parameters. Do this by installing HomeBrew, and then run the following in the terminal:
brew install smartmontools
After installation query the drive using:
smartctl --all /dev/disk0
You will now get the SMART health information for your drive. In particular take a look at the "Percentage Used". That gives a vendor specific estimate of the life used based on actual usage and a prediction of life time. It does not mean that the drive fails at 100% (the value can be more than 100), nor does it guarantee that it does not fail before reaching 100%. It is after all an estimate.
For example my Mac Mini shows that 36 TB data has been written to it (translates into 9 months of usage for you if your numbers are correct). This translates into an estimated 1% used. Had I used that 1% over 9 months, then it would translate into an estimated life time of roughly 75 years.
NOTE: My Mac Mini has the 2 TB version of the SSD, not the 512 GB version you have. The 2 TB version is expected to have a much longer life expectancy than the 512 GB version - so you cannot use my numbers for your drive. You have to check your own drive.