Well, first of course, you will need to make sure that the razor is truly shave ready. Assuming that, you are correct that it can be maintained indefinitely with touch ups.

Based upon what you posted, I assume that you are referring to AJ's stones on ebay. About three years ago those were suddenly all the rage and many here purchased them from him. Grit ratings for natural stones, however, are at best meaningless and can be downright misleading. (Not a knock on AJ, he seems to be a stand up guy.) Most of those stones compare to somewhat lower grit synthetics in terms of the edge we get. Since I have a vintage Llyn Melynllyn I did not try his purple slate but did buy one of his "hard black welsh slate" stones and find that it can deliver a very nice edge. Again, I don't know about his purple slate but the black one gives me an edge that might be a little keener than the LM but perhaps not as smooth. Most people find the Dragon's Tongue to be coarser than advertized and few shave off of it but, rather use it in a progression to another finisher.

Unless you really want to stick with a natural stone, I'd suggest instead the good old 12K Naniwa. It's a good predictable and consistent finisher.

Good luck.


rs,
Tack