diff --git a/.env.sample b/.env.sample
index 9b3c013..fb909aa 100644
--- a/.env.sample
+++ b/.env.sample
@@ -37,6 +37,8 @@ USER_IPS_MAX_AGE=1d
 
 ENCRYPTED_BY_DEFAULT=all
 
+ALLOWED_LIFETIME_MAX=4w
+
 #ENABLE_ALLOWLIST=1
 #FEDERATION_ALLOWLIST="[]"
 
diff --git a/homeserver.yaml.tmpl b/homeserver.yaml.tmpl
index 4eff2f4..2d17939 100644
--- a/homeserver.yaml.tmpl
+++ b/homeserver.yaml.tmpl
@@ -554,8 +554,8 @@ retention:
   # 'max_lifetime' that's out of these bounds, Synapse will cap the room's policy
   # to these limits when running purge jobs.
   #
-  #allowed_lifetime_min: 1d
-  #allowed_lifetime_max: 1y
+  allowed_lifetime_min: 1d
+  allowed_lifetime_max: {{ env "ALLOWED_LIFETIME_MAX" }}
 
   # Server admins can define the settings of the background jobs purging the
   # events which lifetime has expired under the 'purge_jobs' section.