I usually wait 18 months to 2 years before moving to a new version of Windows, when a new version comes out. From past experience that time-frame seems to work.
To avoid having Windows 10 I bought from a reputable store with whom I have dealt for 40 years an OEM Win 8.1 desktop machine as a spare machine and set about updating Win 8.1. Instead of updating Win 8.1 the machine started downloading Windows 10, which I do NOT want. I stopped the download and, when I tried again to update 8.1, once more the machine started downloading Windows 10.
The Windows 10 download was not in any of the 145 updates that Windows 8.1 Update had found.
I returned the machine and got a refund. The store manager told me that the Windows 10 download was compulsory but that the machine wouldn’t actually install Windows 10 without my permission. That doesn’t make sense to me but I have no proof that he was deliberately misleading me.
My main production machine is an Intel Compute Stick, which runs Win 8.1 and works fine but, if Windows 10 is downloaded to the Intel Compute Stick, the Intel Compute Stick won’t work at all since there is very little space on the MMC drive. There is enough space on the MMC drive to use the Intel Compute Stick but it doesn’t have enough space for the Win10 download.
How do I stop the download of Win10?
I followed the instructions in http://www.howtogeek.com/218856/how-do-you-disable-the-get-windows-10-icon-shown-in-the-notification-tray/
In accordance with the instructions on the How To Geek website, I have already uninstalled the KB (KB3035583) that produces the offer icon for Win 10 and hidden that KB when Win 8.1’s Windows Update offered it to me.
Is there anything further to do?
I shall be getting an Android HDMI stick for now as a spare machine, since I can do everything I really need to do in Android.