Pause a keyword when it consistently spends money without generating conversions after receiving enough relevant clicks to make a reasonable assessment. Before pausing it, check the search terms, user intent, landing page relevance, conversion tracking, and cost against your target CPA.
A practical approach is to review the keyword after it spends around 1–2 times your target CPA without a conversion. If the traffic is irrelevant, pause it sooner. If the keyword has strong commercial intent, consider improving the landing page or ad relevance before removing it.
Also, check assisted conversions and CRM data to avoid pausing keywords that generate valuable leads but do not receive last-click credit.