I lost the Leading ignition on one flight (failed ballast resistor in the leading coil assembly) but did not notice it until the next day when I did the preflight checks and disabled the trailing and and leading ignition (one at a time).  The engine quit when I disabled trailing.  I did notice that the EGTs went up about 35 degrees F during that flight when the leading went out. 

 

I use the same ignition timing on both L & T plugs for the reason others have already noted. 

 

 Tracy