Unfortunately, all it take is a complaint to YT with the word "copyright" and they delete the channel.
They may or may not even give a warning to the channel owner.
I've seen it with many channels that I've loved over the years... :-\
I've started downloading videos that I wanted to keep for reference
because you never know when they might disappear in similar fashion..
Most browsers have plugins that will allow you to save YT videos now..
Thanks, Jason. That site is only good for the last three years. The youtube site had older than three years. (Sigh) too bad SolidWorks can't keep the older ones on their SWW site.