A comparison becomes stale when its evidence no longer matches the products. Maintain a claim register so updates change the relevant statements, rather than merely replacing the “last updated” date.
Keep uncertainty visible. If you cannot confirm a feature, label it unverified or remove the claim instead of marking the competitor as lacking it.
Suppose a product adds a free diagnostic. A row that says “paid only” needs correction, but so may a conclusion that recommends another tool solely for free access. Update both and record the evidence date. Do not preserve a ranking whose premise has disappeared.
Distinguish the free domain check from paid monitoring. Verify each monitoring condition and plan limit before comparison. Do not treat public DNS checks as equivalent to inbox tests or aggregate-report analysis simply because all products discuss deliverability.
Use the comparison criteria to keep the reader's task consistent across vendors. Maintain a short change log explaining material corrections so repeat readers can understand what changed.