I'll add that. I've been thinking about it, as there is some gain in sharpness in razors all the way to oxides that go below a tenth of a micron. 1 micron diamond on a razor would be unspeakable on all but the softest of backing (and that's precisely what iwasaki did - soft felt or something with one micron diamond).
I suspect that it will yield little in additional longevity, but I might as well prove it. The draw to 1 micron, though, is simple. It's fast, and it's a replacement of the finish stone rather than in place of. That makes it practical to complete the sharpening process, even when you're in a hurry. I found out when reworking the first back bevels that even with 1 micron diamond, you can't just spend 5 seconds of swashing back and forth and actually get all of the wear out. it's multiples of that. Smaller abrasives will add a step and be slower, but they may add material longevity.