diff --git a/action.yml b/action.yml
index f14d13a..8c245e2 100644
--- a/action.yml
+++ b/action.yml
@@ -283,7 +283,14 @@ runs:
       with:
         name: codeboarding-base-${{ steps.state.outputs.cfg_hash }}-${{ steps.sync_commit.outputs.baseline_sha }}
         path: ${{ runner.temp }}/cb-state/${{ github.action }}/out/base
-        retention-days: 30
+        # Longer than a review's 30 days on purpose, and the margin is the whole
+        # point: correctness comes from the renewal check, which republishes any
+        # base with less than a review's lifetime left, while this surplus
+        # decides how often that fires. Equal lifetimes renew on every run and
+        # publish a base per run rather than per merge base — more storage, not
+        # less. 60 leaves a 30-day reuse window, so a pull request open a month
+        # never triggers one.
+        retention-days: 60
         if-no-files-found: ignore
 
     - name: Publish baseline analysis for the analyzed commit
@@ -293,7 +300,14 @@ runs:
       with:
         name: codeboarding-base-${{ steps.state.outputs.cfg_hash }}-${{ steps.sync_commit.outputs.analyzed_sha }}
         path: ${{ runner.temp }}/cb-state/${{ github.action }}/out/base
-        retention-days: 30
+        # Longer than a review's 30 days on purpose, and the margin is the whole
+        # point: correctness comes from the renewal check, which republishes any
+        # base with less than a review's lifetime left, while this surplus
+        # decides how often that fires. Equal lifetimes renew on every run and
+        # publish a base per run rather than per merge base — more storage, not
+        # less. 60 leaves a 30-day reuse window, so a pull request open a month
+        # never triggers one.
+        retention-days: 60
         if-no-files-found: ignore
 
     - name: Write sync summary
@@ -357,7 +371,14 @@ runs:
       with:
         name: ${{ steps.state.outputs.base_name }}
         path: ${{ runner.temp }}/cb-state/${{ github.action }}/out/base
-        retention-days: 30
+        # Longer than a review's 30 days on purpose, and the margin is the whole
+        # point: correctness comes from the renewal check, which republishes any
+        # base with less than a review's lifetime left, while this surplus
+        # decides how often that fires. Equal lifetimes renew on every run and
+        # publish a base per run rather than per merge base — more storage, not
+        # less. 60 leaves a 30-day reuse window, so a pull request open a month
+        # never triggers one.
+        retention-days: 60
         if-no-files-found: ignore
 
     - name: Render review diagram
diff --git a/tests/test_action_state.py b/tests/test_action_state.py
index 27aca15..95e2ed4 100644
--- a/tests/test_action_state.py
+++ b/tests/test_action_state.py
@@ -482,13 +482,20 @@ def test_the_base_is_inlined_whenever_no_artifact_holds_it(self) -> None:
         self.assertIn("fetch_base.outputs.artifact_id == ''", inline[0])
 
     def test_a_base_outlives_the_reviews_that_reference_it(self) -> None:
-        # A review artifact points at a base by id for 30 days, so a base kept
-        # for less leaves that review unusable for the rest of its life.
-        for step in self._uploads():
-            if "out/base" in step.get("path", ""):
-                self.assertEqual(
-                    step.get("retention-days"), "30", f"{step['name']} may expire before the reviews naming it"
-                )
+        # A review points at a base by id for its whole life, so a base kept for
+        # the same period is only ever good at the instant it is written: the
+        # renewal check would then fire on every run and republish it every time,
+        # which is exactly the duplication that splitting it out removed.
+        review = next(s for s in self._uploads() if "review_artifact.outputs.artifact_dir" in s.get("path", ""))
+        review_days = int(review["retention-days"])
+        bases = [s for s in self._uploads() if "out/base" in s.get("path", "")]
+        self.assertTrue(bases, "no base publication step found")
+        for step in bases:
+            self.assertGreater(
+                int(step.get("retention-days", 0)),
+                review_days,
+                f"{step['name']} does not outlive the reviews that reference it",
+            )
 
     def test_the_reusable_analysis_honours_the_configured_retention(self) -> None:
         warmstart = [s for s in self._uploads() if "warmstart" in s.get("path", "")]