fuel economy is slightly better, I know. for the same reasons you really should go vegan and stop heating in the winter. Personally, I like to live inestead.
less accidents is unproven. Germany has less incidents than NL on highways, so I'd argue that traffic speed limits make you sleepy and annoyed, therefore more likely to crash.
engines already last 300000km ++, so I dont see this as an issue. Your car is outdated on safety tech before it reaches its mechanical limits.
better traffic flow is only imaginary. Those simulations dont take into account how people really drive: They dont increase the distance to one another by such a huge margin as the law requires, therefore more cars can flow at once. It doesnt really make sense to lower the speed of water in a river if you want to increase its total water flow, does it? Also, you cant overtake slow/annoying drivers, so the effective speeds get even slower in many cases when you use artificial limits, resulting in huge chunks of traffic caused by slow drivers instead of makeing full usage of the highway.