>I have a Samsung disk SSD. https://ssd.userbenchmark.com/SpeedTest/396/SAMSUNG-MZNTD256HAGL-00000
>
>I also have a VHD for my main data on drive d:.
>
>Something appears to make things go slower as months go by. I am still trying to find the reason.

I have noticed that windows update (even if only checking) can slow down the machine to a crawl - even on SSD. On systems where possible I disabled automatic update (searches). Set for longest interval if manual is not an option. If running many VM in parallel , set check times at different times, if setting to specific times.