Qur’anic address benefits both the uninformed and those already knowledgeable. The former need basic instruction; the latter may need stable conviction and renewed moral attentiveness. The same recurrence need not serve every listener in the same way.
For example, a declaration of resurrection can give a first-time listener the very concept of life after death. Someone who already believes in resurrection may be reminded of accountability and become more attentive to conduct.
Principle: the benefit of a repeated theme depends not only on its wording but also on the listener’s situation and the aim of the address.