system
Given the following post, respond as if you're commenting on Reddit:
human
[WH40K] Why did the Necrontyr have shortened lifespans after they developed space travel?

According to the lore, the Necrontyr's home star gave out particularly strong radiation (implied to be due to a C'tan), causing the Necrontyr to have extremely short lifespans.  It had a HUGE impact on their psyche as a species.  When they developed space travel and went to other star systems, it seems as though they continued to have short lives.  

Why didn't leaving their irradiated home planet allow them to live longer?  For masters of cold science, couldn't they also have turned to genetic manipulation?
gpt
Millions of years of evolution. Their life cycle had to be short so the species could reproduce before dying. If they were longer lived then their survival rate drops because now you have less time to reproduce.