^ What Chris said. There's a well-known trick of "breaking in" new acoustic guitars by setting them up with a loudspeaker directly up against them and pumping them with music for a few days. I've never tried this myself but a good mate who I trust has done it and reckoned it really opened up the sound. I should try it one day and see what I think.
As a guitar tech for the last 8 or so years I've seen a fair few guitars that have been "stored away in teh case, nice n safe!!" and come out with de-lammed fingerboards, warped necks, rust/mould etc etc. If something is in it's case and not used for a while (which does happen with studio axes) they need to be properly stored with a lot of moisture absorbers in a good stable climate. Like, say, a studio ;-)
I personally think it's actually safer for regular instruments to be in the air as long as the studio is semi-climate controlled, i.e. at least an insulated room - again, like a studio. As long as it's not going from bone chilling cold to blazing heat/humidity then they're fine to be out of the case long term.
Just don't mount them on the wall directly under the main AC unit, as one customer of mine had done. Guitars don't like that....
The other factor to remember is that the strings do generally go off quicker in open air, so it's always good to have a quick peek before a session. I've been to too many studios where their rack of house guitars are all missing important strings, or the strings are rusty as ****
