Al, you mention that you don't have anything safety wired and haven't experienced anything important coming lose in a car.  I have and it was very important. It was a tube and o-ring related to the coolant system that was held into the block by one bolt.  Needless to say the one bolt backed out, I lost coolant over heated and I

 pulled over to the side of the road.  I cannot pull over in a plane.

Don’t misunderstand.  I’m not arguing the point nor suggesting carelessness.  Did you put in the bolt on your car that came out?  I’ll bet not.  I considered every fastener in the engine compartment and torqued and/or locked as I deemed necessary. I exercised care and engineering judgment. There are lock nuts and lock washers as needed. The pan bolts have lock washers. The oil drain is a tapered pipe thread – no way that is coming lose.  I have also periodically checked every bolt, nut, or plug, hose clamp, screw, whatever; and none have ever loosened – so I’m quite happy with it.  Your mileage may vary.

Al G