they are based on mantises right?
mantises literally have 12+ month lifespans, and since they have biological organs to support a larger size like a skeleton, extra muscles, lungs and heart, etc, that would also greatly boost their lifespan to that of a human more, coupled with them also living on a non hostile environment as well making it easier to live beyond than expectations [well before the viltrumites arrive and turn them into sex slaves]
and plus they are an interstellar race or semi because they have vehicles that can travel to earth within a week or less, wouldnt that mean they would also have the technology to also boost their lifespans to?
well I’m not saying take vitrumite genes and clone it to make supers tho it would be interesting, but just any method to extend the lifespan of the thraxans to be that of a human or more.