Hard Disk Monitoring

The health of my 256GB NVMe SSD disk has been declining over time and is now at 63%. I ran a short self-test, but it doesn't appear to complete. At least it goes way over the estimated two minutes to complete and I stop it after 12 minutes of testing with no final result.

I have no real problem as regards backups of this disk because I take image backups daily. However, when the time will come for me to replace it, I would like to be prepared for it rather than have it happen entirely unexpectedly. In your opinion how far down would the health number go before I should seriously consider immediately replacing this disk?

EDIT: I left the test running for over 8 hours! It was still not finished, and I cancelled it. Running Windows 11 Pro and HDS v.6.10.1 (latest beta).

Generally it is recommended to consider/plan replacement when the SSD Health drops below 50% (when the status displayed as yellow) and (as last case) replace immediately below 25% Health (when the status displayed as red).

Depending on the age and performance (as most SSDs already suffer performance decrease around 50%) and importance of the data, you may replace sooner, just to be sure - especially in a critical environment.

The short self test, extended self test (as already discussed in this forum and in the Help) run "inside" the disk drive (hard disk or SSD) when the device is idle, does not need to perform other actions.

It is completely normal and expected that these tests run for MUCH longer than estimated: any disk activity (caused by the operating system or any background software) can delay the test. Yes, it can run for several hours or even more. The estimate (as estimated by the manufacturer) would be valid only if there would be absolutely no disk activity.

So if the short self test, extended self test runs for longer period, it does not mean any problem with the disk drive (or Hard Disk Sentinel) it just means that the disk drive can advance very slowly with the test.
This may indicate intensive background disk activity (maybe writes too - which could degrade the SSD).

Thank you very much for your reply which is quite clear and very informative as always. I'll be watching the condition of this disk drive very closely from now on.