Two categories here: age segmentation for marketing and document management for practical security, and mixing them is a fundamental mistake.
The behavior of verifying documents depends on risk awareness and concrete experience, not broad demographic generalizations.
Someone who has missed a flight in Frankfurt due to an expired passport will develop a rigorous discipline, regardless of their age.
It is preventing concrete troubles, like delays at customs or boarding refusals, that motivates anticipation, not vague “travel stress”.
In Germany, rules are rules, and respecting administrative formalities is a matter of common sense and individual responsibility.