The following is not pontificating, just friendly hangar flying. FWIW.
When an ignition module or magneto coil fails in flight, very few pilots will notice it. A small drop in RPM signaling the failure is usually met with a throttle correction and the pilot continues the flight. Only when the mag fails with a noticeable roughness does the pilot consider doing a mag check in flight.
Almost all pilots do an engine run up and mag check before takeoff. But how many do an end of flight ignition check?
Here's the scenario... You taxi in and shut down the engine in the usual way. Either pulling the mixture, or turning off the ignitions at the same time. The engine shuts down as expected. Unknown is one of the mags/modules has failed. It runs just fine on the remaining ignition.
You park the airplane and look forward to the big fly in just five days away. Wouldn't it be nice to know now about that bad mag/module now instead of getting the bad news during your next run up?
There's no need to do a run up at the end of the flight. Just do a quick mag check at idle power. You'll avoid bLowing dirt around the ramp and if a mag is inop, you'll prevent a backfire.
For engines that shut down by pulling the mixture be sure to check the both off position, too.
I hope this will prevent someone from cancelling a flight because they didn't know they had a bad ignition at the end of the last flight.
John P