^ not sure where that comes from, but not universally true.
You can keep repairing diamond cut wheels, as long as there is enough metal to keep cutting (removing) from the face, not to compromise safety or aesthetics.
Each wheel style is different, but you can usually get around 3 passes or repairs out of a wheel.
The repair, once done, is permanent, and once lacquered again, will last as long as an OE wheel.