That's true. I guess I also spent a lot of time observing our two airplanes, the C-206 an the C-320. You wouldn't call them equivalent airplanes but they had virtually the same engines. It seemed like things had to be replaced much more frequently on the 320. However, when you think about it, it makes sense because if a part would normally last x hours and you have two of them you would need to replace both within a certain time frame on the twin but only one on the single. I realize that it doesn't apply to all parts, such as the avionics. However, you normally have double the vacuum pumps, fuel pumps, magnetos, voltage regulators, alternators, turbochargers, etc. on a twin, not to mention the engine and the prop. Obviously there is going to be a premium that you pay for maintenance on a twin.