I'll be honest - I live in Scotland where there is a lot of mositure in the air, it's a damp climate. Oh and we have gas central heating to keep warm - it won't dry out the air - that's a dehumidifier and people don't use them daily.
The temperature fluctuates daily here from being warm, to cold and windy. From years of owning electronics gear, the climate hasn't harmed anything thus far. I have noticed that apple product owners are really really anal about the little things for example the tiny bit of condensation behind the glass of an imac, the temperature of macs, what's the best thing to clean my imac, the list goes on...relax people.
The product works as expected. Spend less time worrying about the intricacies of the imac and more time using it to be productive. These things are tested to various limits and I reckon my house is well within the extremities of these.
Anyway back to my previous post - pointless getting a new one as it'll happen again, such as life, such as science