Given the low life expectancy and the brutality of battles in ancient times, I am quite surprised by his career.
Source: Parker, Geoffrey, and Victor Davis Hanson. “From Phalanx to Legion.” The Cambridge History of Warfare, 2nd ed., Cambridge University Press, 2020, pp. 31–46.
That's pretty long, but a career soldier was expected to serve long enough to, well, make a career out of it.
u/amp1212 talks about the likelihood of surviving the typical 25 years expected of a career soldier. More can be said, especially since your example is from the earlier Republican period. Notably the service length was extended occasionally, meaning there were enough soldiers coming up on retirement that were still in fighting shape that it was worthwhile.
Obviously it depends strongly on when you served and where, but serving in the military, then and now, is not a life of constant battle.
Life expectancy is a commonly misunderstood measure. In the ancient world, actually in basically all of human history until quite recently, being born was about the most dangerous thing you did. I'm only kind of joking - it varies across time and place but it wouldn't be too wildly inaccurate to figure that half of all children ever born have died in infancy or before reaching the age of 10. Life expectancy is an average, so having all those young deaths drives the average down. Compared to now, life even for a healthy adult was much more dangerous (in particular, disease), but once you survived childhood your life expectancy wasn't so bad. Soldiers, being healthy adults with access to food and water and often away from the cities (where disease spread more easily and sanitation was more of an issue) were in a pretty good situation...well, as long as they didn't die in battle.
Now just how dangerous were ancient battles? u/iphikrates discusses this for classical Greece, which is earlier than your soldier, in a whole different culture fighting a different kind of conflict. Still, I think you'll find it informative. And remember that casualties were not necessarily fatalities - obviously medicine was nowhere near as good as now but injuries that rendered you a casualty could still be survived.