Like most things in nanotech, assemblers are a big topic. Is an assembler even possible? What do we need to do to develop them? Who is working on them? When will we have them? And what will we be able to do with them? That's too many questions for one essay; I'll focus on the technology required to build one, and by extension, the schedule we might see. The point of this essay, as the title implies, is that it's impossible to give a sensible timeline for the development of an assembler."