Are repetitive mild aspiration pneumonias, life threatening? Recovers fast with antibiotics and oxygen.

Not good. I ask why. Do they occur at night(gerd), do you have trouble swallowing, hiatial hernia;perhaps overweight. The fact that this is occuring, and that you recover fast does not mean that you always will. Should these episodes become more severe and as you get older, your treatment options may become limited. Get the cause worked up and decide what to do with you pcp.
Potentially. If someone was chronically aspirating the concern would be that is a large amount of stomach contents was somehow aspirated the lungs would be more severely injured and a worse pneumonia could occur. Therefore most of the time the cause of the aspiration pneumonias would need to be addressed or the underlying problem be solved, for example if there is a swallowing problem it would need to rx.