Nobody reached 30 in the Middle Ages – that's a maths error.
The low life expectancy of past eras is an average dragged down by high infant mortality. Among the English peerage it was 30 to 33 years at birth. But someone who reached 21 could on average expect to live into their mid-sixties, and around 1500 to roughly 71.
Useful: With any average, ask which extreme values are pulling it around.
Source: en.wikipedia.org