I don't. You're asking the wrong question.
You stated that the "risk" of an engine failure is small. It's not. It's a big risk, and perhaps until you have one, or several, then it's an academic one.
You have the same "chance" every time; the engine will either run, or it won't. Better put, it will run properly, or it won't. My last event resulted in a forced landing on the side of a mountain with an engine that was fully responsive to the power lever, and a propeller that wasn't. No oil. While the engine ran fine, it did me no good...so perhaps it's better to say either the engine will work for you, or it won't.
I don't care about five hundred hours, or five thousand, or dividing failures into those hours. I've gone for years without failures, and then had multiple failures in a year or a season, in multiple aircraft for multiple operators. There's really never been anything "average" about them.
The attitude of assuming it's a "small risk" is a dangerous one. I used to think it was a small thing too. After you've made forced landings off field, after you've dealt with some of the things that can go wrong, truly wrong, with an airplane or airframe, then you'll come to appreciate the fallacy of that concept; it's not a small risk, at all. It's very real.
Fly over the freezing water to get to that meeting if you like, but it's not a "small risk." That same flight could be made over the shore, perhaps...taking longer to get where you're going, but with options in the event of a power loss. You could take that flight out in the middle of the night through the mountains and possible weather, or wait until morning so you have options. Me? I wait for morning. I follow the shore line. I stay over roads. Risk elimination is all about identifying risks and eliminating them by avoiding what causes them, or providing a way out, options, so it's no longer a risk.
Accepting risk is to embrace hazard, to marry chance, and to lie with a question. It has no place in aviation, particularly not in private aviation.