Thanks. Very interesting.
The estimate from the video was that about half survived until retirement (25 years of service). I’d be curious what most of them did afterwards.
If they qualified for land (which wasn't guaranteed) in a favorable part of the Empire, they might take that, or flip it and go back to a place they preferred.
Often the retirees would settle in an area where they had married. Marriage was fairly common though officially against the rules.
If they had married, they'd sometimes be able to avail themselves of a farmstead they'd either paid for years earlier, or as a sort of dowry from the wife's family.
More probably left service or were released, after surviving some major campaigns, and had to fend for themselves, iow, no retirement per se. When the Pompeian Civil War ended, mobilization seems to have continued.
When the sordid self-serving assassins of Julius Caesar recruited and trained, large armies continued to accumulate. Even after they were defeated and destroyed, training and recruitment probably continued to rise due to the territorial turmoil going on during the Second Triumvirate.
After Lepidus got caught doing some shady crap with some of his old colleagues from the Pompeian War days, the power structure suddenly became divided in two factions, which lasted until the defeat and deaths of Antony and Cleo VII.
After that, Augustus consolidated legions, cut the number of regular legions in half, and introduced regular standing legions of auxiliaries. The Roman army then consisted of 28 regular legions, 28 auxiliary legions, and one legion of Praetorian Guard (they were the city's police force as well as the E's bodyguard).
At some point (not sure if Augustus did it, or someone later, and am too lazy to look it up) the size of each legion was reduced slightly, and the centuries were reduced in size to 80 (from 100, but they kept the name) to create more upward mobility among officers. By the 2nd c, the Roman army consisted almost entirely non-Roman, but were culturally assimilated to quite an extent.
Those who left service without retirement waiting probably greatly exceeded the number who died in service. Familiar with the needs and wants of soldiers on campaign, it would be surprising if there weren't a good many who made a second career out of selling stuff to the Roman army or local soldiers. Also, when they needed some cash and Rome needed some experience soldiers or trainers, they'd pick up a few bucks.
Of the survivors, some would have to leave services in a disabled state, and take up some kind of shady trade to survive their remaining years.
They got lucrative jobs in aerospace companies
“I’d be curious what most of them did afterwards.”
Bought a bar in Miami.