Wow, Jim, lots of questions…
Depending on how long you play, and depending on what kind of flute you have, swabbing won’t always be required. My German flute (narrow bore) tends to get damp quickly, whereas the Pratten-style Hammy – particularly in drier times – will not get too moist, except maybe in the headjoint, for the first fifteen minutes to 1/2 hour or so. The best bet would be building or buying a stand that allows you to safely leave your flute upright between plays. What you don’t want is lots of moisture gathering in the joints, but short plays will not do this. Overnight, definitely put it away.
I wouldn’t leave a wooden flute in a car trunk for a number of reasons. The heat extremes is the most obvious worry (too hot in the sun, too cold in the winter), but if you put your flute, in case, inside a thermal cooler, you can offset all these extremes. So, that’s one way to avoid worry. BUT living in NYC, though, my biggest fear would mostly be the loss of said flute – I wouldn’t leave any instrument (and, for me, any instrument over a hundred dollars is too costly to lose) in a car. I was a working guitarist for the better part of my adulthood, and I never left guitars or amps, etc. in trunks, either, even though temperature was rarely the worry (except for superficial things like the wood finish cracking on an electric.)
NYC apartments get very hot and dry during the winter. I simply put the flute case inside a wooden box with something damp outside the case; lots of air exchange, so no mildew, and – since I play fairly often – the flute is pretty humidified inside it’s own case. Takes awhile for everything to dry out, and by then, I’m playing again. Also, for my own health as well as the piano, the guitars, other assorted instruments and plants, I ran a room humidifier all winter. Man, I’m glad we’re on the summer upswing now…
The Hamilton is in a Cavallaro soft case, which is basically a nylon case lined with artificial (polyester) fleece. So humidity stays inside fairly well without being sealed like a baggy and the fleece keeps the flute from really rapid temp changes. I also carry it inside my coat when going outdoors in the winter. My German flute is in a wooden case I made myself, and I’m much less fussy about it’s care than the Hamilton. It used to be my regular flute, and has been out in all weather, and never cracked on my watch, either.
What else… Oh, subways. Well, I’ve done less busking lately than I used to, but in the fall, winter and spring, the tunnels that link the stations get pretty cold, easily 40deg. or so; the flute drips like a faucet! People stream by in an unceasing flow and you usually have to back up against the tile to avoid being knocked over. The best spots in the system are usually taken by those performers who bothered to apply for a licence, which are free but you have to audition for the MTA, and you can get ticketed if you play those areas without a licence, but you are left alone if you find a less visible spot. Portable amps are allowed everywhere except on the actual train platforms (the MTA claims they interfere with the unintellible garble that passes for important announcements), but in the tunnels a flute carries fairly well without one, anyway.
I’m sure I missed something…
Well, if I did, you let me know.. 
All the best,
Gordon
) but I’d have no problem taking my German flute, fully keyed, which is wood and seems to have survived about a century unscathed.
, I still think the musical end of things leans heavily in favor of a good wooden flute, and ultimately, I care more about the musical end of things than the instrument’s durability. Try telling a player of a top of the line Martin guitar that the round-back Ovation is a better instrument! Still, on the road, I’d rather bang the Ovation than crush the Martin.