It's been awhile since I've used any AC, being winter and all, but when you put it on (even in your home), don't you leave it running even when you leave? It wouldn't make sense to turn it off everytime you leave the house because it would take quite a bit of time to cool things off again upon your return (creating larger electric usage than if you had left it on). I can see if you leave for days or something, but when I go to work in the summer, I will leave it on low no problem. It's just our preference in our home.
Furthermore, on a cruise, I definitely leave my ac on when we go to the pool, dinner, whatever because of the same reason.
What I was asking about in reference to using a magnet just enables me to continue to have a cool-enough room while also having the balcony open for a bit.
When you think about it, most people probably leave the AC on during most of the cruise, so I extend that AC units in the majority of cabins are running a majority of the time. What difference does it make if my AC runs as well, albeit with the balcony open? I would have had it on anyway.
Lastly, how is any of this selfish?