Lost of newer pilots who are out shopping for a plane look at the time since last major overhaul and the suggested TBO. Thinking, "Hey this engine obnly has 900 hours on it, now I can fly for another 1,000 before having to worry about anything."
But there are two little items in your engine that are made of plastic,,,, and if they break or quit working in flight you are in for some interesting times.
I speak of your MAGNETOS.
Yes you have two of them, but oddly enough a local air 135 operator had two occasions in the 2 years when both mags failed.
I look at mine very year...and I just caught one that had gone bad , yet it was still working.
The mag in question had about 550 hours on it and as said it still worked fine and tested fine... But a visual inspection showed that the carbon brush on the end of the rotor had been fried from arcing. In other words it SHOULD HAVE NOT BEEN WORKING AT ALL.
And this mag looked fine during another inspection 50 tach hours previously.
One photo shows the old assembly on the left with the new assembly on the right. The other photo shows the bad Rotor assembly with the damaged shaft. There is supposed to be a spring-loaded carbon brush on the end of that shaft. It is now welded into the end of the shaft.
Years ago I had a mag fail in flight. It turned out that one of the P-lead connector had been damaged by somebody who was cleaning planes. It worked OK until the heat and vibration made it connect only at odd intervals.
So long story short,,,, while an engine may go for a long time without a complete overhaul, the Mags are just plastic parts that should be changed a lot more often.