Another praise for the DiaFlat. I've had mine close to a year and a half and have lapped every stone I can think of, except for a carbo. I even lapped out deep chips from a 00 with no ill effect.
The only sign of wear on mine is on one edge where the diamonds have let go, but this has no effect on its function and admittedly I've used way more pressure than I should have several times. If mine died today, I'd buy another one before the sun set.