Aren't you the person that started a thread because he carries an external battery so as not to use a laptops battery, increasing cycle count and theoretically, reducing resale value? Then started a thread about getting a keyboard protector for his Air because he was worried about shiny keys from use reducing resale value? And that a MacBook Air 15 is too large you would rather carry an external monitor?
This concern is an example of a little knowledge is a dangerous thing. We can second guess Apple's engineers I suppose, but by and large they know what they are doing, and the Air's power is balanced against the heat it generates so as not to cause failure. They Air is designed to be the ultimate Mac for portability, I dont think many want a fan in it. Then it would be larger and bulkier.
You do worry a lot. These things are tools to be used. Enjoy.