Personally, I find it hard to see how twenty more years can pass without people being able to make planet-killing nanotechnology, so I give it twenty years maximum before we're in the endgame.

This seems to be an extraordinary claim, but it doesn't seem anyone else has commented on this. Admittedly this is somewhat tangential to the main point, but I wonder if this is the common educated view on the subject.

My own general expectation was that self-replicating nanotechnology would take several decades at the low end and possibly more than a hundred years, in the absence of an AI singularity.