That is true but leaving the air vent on requires a lot of electricity. (a rediculas sum)
And having only the cockpit then makes the air go away pretty fast (around 10-15 minutes).
Not noticing it resluts into dying and probably losing your miner.
Having to setup a timer block to the air vent is just to much trouble for the little function but i do agree i better might have added an oxygen tank instead of generator. then you can fill it up from your base when you dock and probably have oxygen to last longer then you are able to play.

Put a vent on you cockpit. That is the same as opening the window. However, oxygen support makes it useful on low O2 planets.

Thanks man!