Research on the stability of temperament indicates that it is unstable and subject to wide variations over the course of a lifetime unstable during childhood but stabilizes during adolescence and remains stable throughout a person's adult life relatively stable through the first three to four years of life but begins to vary dramatically once a child reaches school age relatively stable well into adulthood

relatively stable well into adulthood

Explanation:

Temperament is an individual's character or nature which greatly affects the behavior of the individual.

Temperament develops gradually over time. During early childhood, individual differences can be seen in distress proneness, attentional orienting, positive approach, positive affect and frustration. However, temperament does appears to become more stable during the adulthood or late adulthood ages where people are in more control in their personality trait.