That doesn't change my advice to folks to find a co-founder.

Right, but you're not advocating the "stop the world" and do nothing until they do find a co-founder, are you? I guess that's my point: a solo-founder isn't necessarily somebody who intends to stay a solo-founder, but are likely someone who just hasn't found their co-founder(s) yet. And I, for one, would not advocate stopping everything until you find that person (or persons).