Those chinese stones are a bear to lap, but once done you shouldn't need to touch it again for quite some time if you are only using it on your own razors - depending on how much you use it, you may never have to lap it again.
Unfortunately, prolonged lapping on a 325 DMT with a stone like this will really 'tame' the plate, and it will take longer and longer to get the same results. If you don't keep flushing the slurry away (or lap under a running tap or under water !) you run a real risk of undermining the matrix and losing the diamond layer. In my opinion DMT plates are best used with softer stones, and 325 is the highest plate you should use.
Other DMT 'killers' include any of the novaculite-rich stones such as turkey stone, washita, arkansas, charnley. Spydercos turn their noses up at DMTs, too. A DMT is certainly not the be-all and end-all option that it is sometimes made out to be! And they do wear out - the ragged ends of the diamonds wear away (a good thing: you should hone scrap steel on them for a while when new in order for this to happen) and after sometime they become quite slow - my first DMT still sees occasional service, but it is nowhere like a 325 plate, more like 600 or even higher and its replacement is already slowing down - but I do hone up to 20 razors a day (a lot need major surgery!) on occasion plus leather cutting equipment and other tools.
The cheapest and fastest option (faster than a diamond plate) for lapping hard stones is lapidary grit in a range of grit sizes and a stout plate of glass. Put a bit of the grit on the glass, add some water and lap away.
If you are going to be doing a lot of razors, ditch the c12k - it is way too slow - and get something like a naniwa 10k or 12k - DMTs don't break much of a sweat lapping these, but be sure to frequently rinse away the slurry for the reasons already stated and keep them plenty wet to avoid the dreaded 'stiction' (plate and hone stuck together by suction).
As far as lapping higher than 325 goes, I think it works - in a limited way. However, even shapton recommend their 325 grit lapping plate for their 30,000 grit glass-stone.
Regards,
Neil
