великовозрастный

Etymology
From.

The change in stress from to  occurred as a result of the banalization process. The wordform was formed according to the rule of forming compounds, where a complex bracket is formed if the second part is more than one syllable, and the stress is placed on the last syllable of the stem. But as a result of banalization, in modern pronunciation, the second part of the compound does not obey the old rule and retains the stress in the same place as in the non-derivative word. The modern stress pattern was probably first recorded in in 1935.

Also found in colloquial speech when asked to repeat the word. This wordform seems to have been re-analyzed using the compound with loose attachment of morphemes.

Compare with which in modern usage developed an additional stress pattern  even though the original stress pattern continues to be used.

Adjective

 * 1)  overage too old, no longer a child