I understand that you care about the health of your instruments but, believe me, those Gretsch are built like tanks. The massive top is so solid that I had to venture around various sets, during a span of more than two years, to find the strings that will make this heavy soundboard ring with the right amount of avibrations... Plus, I live in a flat with electrical heating, which results in a very dry air and can be potentially harmful for any instrument. Yet, I never had any cracks or problems with any of my guitars. My guitalele is roaming in various places on my office deck (it feels so good to sight reading the scores I find everyday on the web!), wich is located at less than 2 meters from the heater : no problem, not even the need to tune it every morning.
Oh, yes, I have one tip to make things easier with the dry air : I always leave a sponge floating in bucket full of water somewhere in the room : this is very effective — and by the way it absorbs wonderfully the cigarette smoke...
It's important to keep a good amount of humidity in the room where you keep your instruments but, as you see, it's not so difficult — unless you live in an extreme weather.
PS : no sound sample for the moment, but I'll do my best to post one in the next future. And welcome home if you come to Paris !