Doppo is saying that once people live for over 50 years, they've already got to meet many sorts of people. He means that by age 50 he'd already met them. It can be a little bit confusing by the wording, but the logic is still in place, unlike the time in the Gaia fight when the general talked about "a war in 1980 and then 30 years later".
In another note, that is not how a 5 year old looks like