diff --git a/services/grafana/prometheus.nix b/services/grafana/prometheus.nix
index 4ac8bd5..680ca3d 100644
--- a/services/grafana/prometheus.nix
+++ b/services/grafana/prometheus.nix
@@ -21,7 +21,7 @@ in
     port = service_configs.ports.private.prometheus.port;
     listenAddress = "127.0.0.1";
     stateDir = "prometheus";
-    retentionTime = "90d";
+    retentionTime = "0d"; # 0 disables time-based retention (keep forever)
 
     exporters = {
       node = {