I'm not sure whether the component degradation thing in relation to a hood louvre can be 100% proven or not.
While I know that heat cycles will destroy things like plastic over time, the louver isn't by any means getting rid of the extreme temperatures under the hood. Cooling it down a bit? Sure. But not so much that the plastic parts aren't still being subjected to heat cycles.
Having said that, I'd have to see some sort of long term controlled test with two identical vehicles driven over X amount of years, one with a hood louvre, one without. My guess is that any components saved from degradation would be negligible at best.
I'm not saying it's not possible, I'm just saying without some serious real world data, I don't think you'd really be saving any of your plastic components.
But as far as looks go, I get it! Some guys just dig the look, and I can totally understand that!
Forgive me, I'm just being the skeptic in the room.