Using a little rubber-bulb type air squirter is likely to introduce MORE dust into the driver, not remove it. And besides, you can't get at the driver anyway- it's inside a set of dust seals. Lightly blowing some air into the earcup will do NOTHING to the driver. It's sealed away in it's dust envelope.
Stax drivers are sealed within a dust shield, kind of like a plastic bag around the driver.
Besides, dust levels in a normal domestic environment are not terribly high and thanks to the dust seals dust doesn't really get inside the drivers. I don't cover any of my headphones. They all continue to work just fine. I don't think there is any more reason to worry about Stax headphones and dust than with any other gear.
If you thought there was dust inside your Stax drivers, you'd have to tear open these dust seals, and then dust the drivers with DUST FREE dry gas (i.e., technical grade dry nitrogen) in a DUST FREE environment such as as an ISO Level 6 or better cleanroom to be assured of success. If you have the $1 million to build the cleanroom, then by all means proceed....
Then you have to replace the dust seals, for which there is no known field procedure.
While I have heard of people taking apart a Stax driver and repairing it at home successfully, I have also heard of many failures when trying this. If the driver is already BAD, well there's nothing to risk. But if you are trying to IMPROVE a working sub-par driver- gee- GOOD LUCK!
Really high humidity and hot weather CAN negatively impact all kinds of transducers- not just Stax drivers. When it comes to Stax drivers, high humidity MIGHT cause the diaphragm coating to break down, and it can also weaken various adhesives used in various places in the driver and the headphones. Poorly coated diaphragms will lose efficiency, and things like channel imbalance and maybe even distorted sound could result. Only fix is a new driver. Some folks have re-coated the diaphragms, but a recoated driver will have different electrical and acoustic characteristics, won't be a Stax driver (though it might be close in performance if you are really lucky and highly skilled.)
If there is dust inside the driver, the most common symptom is squealing, hissing or a kind of "crying" sound. Koss electrostatic headphones sometimes come from the factory with a dust mote installed in a driver...and they will do some squealing and hissing, it's a fairly quiet sound but it is definitely audible. I think maybe Koss doesn't have a cleanroom for electrostatic driver assembly. I worked at Koss in 1976 and I don't remember a cleanroom, I remember them assembling ESP-9's out in the factory. But maybe the drivers themselves were assembled elsewhere in some kind of cleanroom, I don't know. What I DO know is that if you buy ESP-950's and one or both drivers squeal, you can send them back and Koss will replace them, Koss offers a lifetime warranty on their electrostatic ESP-950's.
Channel imbalance is typically NOT caused by dust, but by something like element spacing being out of tolerance, or some problem with the diaphragm coating. I do not know of anyone who has successfully fixed an imbalance-challenged Stax driver at home. Problems with wiring, soldering and so on might also cause channel imbalance, although I would guess these causes to be rare.
Dust in the amps? Well, dust gets into electronics all the time. Pots get scratchy, connectors get noisy, in tube gear, tube sockets grow microphonic and so on. Don't store electronics in a woodworking shop, stone quarry, coal mine, fabric production environment or other high-dust locations. If your amplifier is kept in a normal home setting, it's probably a good idea to open the amp chassis up every 5~10 years and hit it with a little "canned air" dust removal product.