I hate to say the obvious, but 27 year old solders are better training investments than 17 year olds. You will find reservists crash less trucks, cars, bulldozers on the way to the fight. Im 53, awaiting the offer to go build and fly drones for the Ukrainians. Since a good 7 inch drone pilot can turn around a platoon of .7M dollar tanks just as fast as an A10, my rate is 180k US per month.
And it's better on the demographics too. 27 years old soldier may have a kid or two. So if he gets killed, at least he will be able to continue his legacy through his progeny.
In the Vietnam war of the 58,000+ killed, Of those killed, 61% were younger than 21 years old. Given that a large percentage of those under 21 were typically Infantrymen gives backing to the average infantryman in the South Pacific during World War II saw about 40 days of combat in four years. The average infantryman in Vietnam saw about 240 days of combat in one year thanks to the mobility of the helicopter.