harmonic balancer

how long can you drive with a harmonic balancer rattling before you tear up the threaded part of the crank shaft?

and can you repair the threads with a sleeve?

The balancer is keyed on the crankshaft-- the threaded part is for the bolt that holds the balancer on- the threads should never tear up-- and if they did- the car would not run- because the crank position sensor would be off- if the key did not hold it at the right spot.