Maturity, reliability and precision are important for transmitting a report, but no one age in years is an absolute qualification for every person. Capacities vary among narrators.
Some scholars favored narration after a more settled age, such as forty or fifty. That preference does not make all younger narrators unacceptable, nor does greater age establish accuracy automatically.
The real requirements are accurate preservation, fitness to deliver the report, and the relevant standards of narration.
An insufficient test is relying on a date of birth alone to determine truthfulness or accuracy.
Chronology supplies evidence, not a substitute for critical investigation.