Not always true, but generally speaking, yes. Air density will necessitate some fine adjustments occasionally, depending on how stable the weather in your location is. A fine, dry (non-humid) day in the South is relatively rare, but on those occasions the mixture needs to be richened a tad, conversely if you're set for arid weather, and it gets muggy-humid, like August in Charleston, SC, then you might need to lean the mix because the air is less dense then.

This summer here in NC has been like that. June came, was way wet, then it dried out enough that I had no rain, zip, nil, nada, at my house for two months, and the humidity (normally around 60-75% here) dropped into the 35-40% range, and was significant enough to require retuning several clicks of the needle on all my Saitos.