diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index 436c277..dcd926a 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -5,7 +5,7 @@ import ShowsPage from "./pages/ShowsPage";
 import TimeSyncNotice from "./components/TimeSyncNotice";
 import "./index.css";
 
-const TIME_SYNC_OFF_THRESHOLD = 500;
+const TIME_SYNC_OFF_THRESHOLD = 200;
 
 export default function App() {
   const [open, setOpen] = React.useState(false);
diff --git a/frontend/src/components/TimeSyncNotice.tsx b/frontend/src/components/TimeSyncNotice.tsx
index e9cd815..57f97dc 100644
--- a/frontend/src/components/TimeSyncNotice.tsx
+++ b/frontend/src/components/TimeSyncNotice.tsx
@@ -16,22 +16,57 @@ export default function TimeSyncNotice({
     thresholdMs = 500,
     intervalMs,
     lang = "ja",
+    dismissTtlMs = 5 * 60_000, // ✅ reappear after 5 minutes by default
+    storageScope = "session",   // "session" | "local"
 }: {
     thresholdMs?: number;
     intervalMs?: number;
     lang?: "ja" | "en";
+    dismissTtlMs?: number;
+    storageScope?: "session" | "local";
 }) {
-    // removed `error`
     const { skewMs, rttMs, recheck } = useTimeSkew({ intervalMs });
 
+    const KEY = "timesync.dismissedUntil";
+    const store = storageScope === "local" ? window.localStorage : window.sessionStorage;
+
+    // read dismissed state (true if now < dismissedUntil)
     const [dismissed, setDismissed] = useState<boolean>(() => {
-        try { return sessionStorage.getItem("timesync.dismissed") === "1"; } catch { return false; }
+        try {
+            const raw = store.getItem(KEY);
+            const until = raw ? Number(raw) : 0;
+            return Number.isFinite(until) && Date.now() < until;
+        } catch {
+            return false;
+        }
     });
 
+    // auto-unset when TTL passes (while component stays mounted)
+    useEffect(() => {
+        if (!dismissed) return;
+        let id: number | null = null;
+        try {
+            const raw = store.getItem(KEY);
+            const until = raw ? Number(raw) : 0;
+            const delay = Math.max(0, until - Date.now());
+            if (delay > 0) {
+                id = window.setTimeout(() => setDismissed(false), delay);
+            } else {
+                setDismissed(false);
+                store.removeItem(KEY);
+            }
+        } catch {
+            /* ignore */
+        }
+        return () => { if (id) clearTimeout(id); };
+        // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, [dismissed]);
+
+    // if skew returns within threshold, clear dismissal so it can show again later if it drifts
     useEffect(() => {
         if (skewMs != null && Math.abs(skewMs) <= thresholdMs && dismissed) {
             setDismissed(false);
-            try { sessionStorage.removeItem("timesync.dismissed"); } catch { }
+            try { store.removeItem(KEY); } catch { }
         }
     }, [skewMs, thresholdMs, dismissed]);
 
@@ -47,7 +82,10 @@ export default function TimeSyncNotice({
 
     const onClose = () => {
         setDismissed(true);
-        try { sessionStorage.setItem("timesync.dismissed", "1"); } catch { }
+        try {
+            const until = Date.now() + dismissTtlMs;
+            store.setItem(KEY, String(until));
+        } catch { }
     };
 
     return (