diff --git a/charts/cluster-addons/templates/monitoring/kube-prometheus-stack.yaml b/charts/cluster-addons/templates/monitoring/kube-prometheus-stack.yaml
index a96402c..4e8ef48 100644
--- a/charts/cluster-addons/templates/monitoring/kube-prometheus-stack.yaml
+++ b/charts/cluster-addons/templates/monitoring/kube-prometheus-stack.yaml
@@ -57,10 +57,11 @@ stringData:
         serviceMonitorSelectorNilUsesHelmValues: false
         ruleSelectorNilUsesHelmValues: false
         {{- if $prometheusVolumeSize }}
-        # Set the retention size to 95% of the given volume size
+        # Set the retention size to max 85% of the given volume size, to leave space for the WAL
+        # To get a valid storage request, we round down to the nearest whole number
         {{- $storageAmount := mustRegexFind "^([0-9]*[.])?[0-9]+" $prometheusVolumeSize | float64 }}
         {{- $storageUnits := mustRegexFind "(K|M|G|T|E|P)i?$" $prometheusVolumeSize }}
-        retentionSize: {{ mulf 0.95 $storageAmount }}{{ $storageUnits }}B
+        retentionSize: {{ mulf 0.85 $storageAmount | floor | int64 }}{{ trimSuffix "i" $storageUnits }}B
         {{- end }}
     grafana:
       sidecar:
diff --git a/charts/cluster-addons/values.yaml b/charts/cluster-addons/values.yaml
index 6922959..de12e57 100644
--- a/charts/cluster-addons/values.yaml
+++ b/charts/cluster-addons/values.yaml
@@ -223,7 +223,7 @@ monitoring:
             compactor:
               retention_enabled: true
             limits_config:
-              retention_period: 744h
+              retention_period: 72h
           # Enable persistence by default
           persistence:
             enabled: true