diff --git a/src/monitor/_monitor.py b/src/monitor/_monitor.py
index 750bf1ff5f..e4ad81f3b6 100644
--- a/src/monitor/_monitor.py
+++ b/src/monitor/_monitor.py
@@ -313,7 +313,7 @@ async def _do_monitor_a_feed(self, feed: db.Feed, now: datetime):
                 feed.etag = etag
                 feed_updated_fields.add('etag')
 
-            new_next_check_time = _defer_next_check_as_per_server_side_cache(wf)
+            new_next_check_time = wf.calc_next_check_as_per_server_side_cache()
 
             if not rss_d.entries:  # empty
                 logger.debug(f'Fetched (not updated, empty): {feed.link}')
@@ -362,32 +362,3 @@ async def _do_monitor_a_feed(self, feed: db.Feed, now: datetime):
         await Notifier(feed=feed, subs=subs, entries=updated_entries).notify_all()
         stat.updated()
         return
-
-
-def _defer_next_check_as_per_server_side_cache(wf: web.WebFeed) -> Optional[datetime]:
-    wr = wf.web_response
-    assert wr is not None
-    expires = wr.expires
-    now = wr.now
-
-    # defer next check as per Cloudflare cache
-    # https://developers.cloudflare.com/cache/concepts/cache-responses/
-    # https://developers.cloudflare.com/cache/how-to/edge-browser-cache-ttl/
-    if expires and wf.headers.get('cf-cache-status') in {'HIT', 'MISS', 'EXPIRED', 'REVALIDATED'} and expires > now:
-        return expires
-
-    # defer next check as per RSSHub TTL (or Cache-Control max-age)
-    # only apply when TTL > 5min,
-    # as it is the default value of RSSHub and disabling cache won't change it in some legacy versions
-    rss_d = wf.rss_d
-    if rss_d.feed.get('generator') == 'RSSHub' and (updated_str := rss_d.feed.get('updated')):
-        ttl_in_minute_str: str = rss_d.feed.get('ttl', '')
-        ttl_in_second = int(ttl_in_minute_str) * 60 if ttl_in_minute_str.isdecimal() else None
-        if ttl_in_second is None:
-            ttl_in_second = wr.max_age
-        if ttl_in_second and ttl_in_second > 300:
-            updated = web.utils.rfc_2822_8601_to_datetime(updated_str)
-            if updated and (next_check_time := updated + timedelta(seconds=ttl_in_second)) > now:
-                return next_check_time
-
-    return None
diff --git a/src/web/utils.py b/src/web/utils.py
index 4d7a0703ad..5814da00a2 100644
--- a/src/web/utils.py
+++ b/src/web/utils.py
@@ -221,6 +221,44 @@ class WebFeed:
 
     web_response: Optional[WebResponse] = None
 
+    def calc_next_check_as_per_server_side_cache(self) -> Optional[datetime]:
+        wr = self.web_response
+        if wr is None:
+            return None
+        now = wr.now
+
+        # defer next check as per Cloudflare cache
+        # https://developers.cloudflare.com/cache/concepts/cache-responses/
+        # https://developers.cloudflare.com/cache/how-to/edge-browser-cache-ttl/
+        if (
+                self.headers.get('cf-cache-status') in {'HIT', 'MISS', 'EXPIRED', 'REVALIDATED'}
+                and
+                wr.expires > now
+        ):
+            return wr.expires
+
+        # defer next check as per RSSHub TTL (or Cache-Control max-age)
+        # only apply when TTL > 5min,
+        # as it is the default value of RSSHub and disabling cache won't change it in some legacy versions
+        rss_d = self.rss_d
+        if (
+                rss_d.feed.get('generator') == 'RSSHub'
+                and
+                (updated_str := rss_d.feed.get('updated'))
+        ):
+            ttl_in_minute_str: str = rss_d.feed.get('ttl', '')
+            ttl_in_second = (
+                                int(ttl_in_minute_str) * 60
+                                if ttl_in_minute_str.isdecimal()
+                                else wr.max_age
+                            ) or -1
+            if ttl_in_second > 300:
+                updated = rfc_2822_8601_to_datetime(updated_str)
+                if updated and (next_check_time := updated + timedelta(seconds=ttl_in_second)) > now:
+                    return next_check_time
+
+        return None
+
 
 def proxy_filter(url: str, parse: bool = True) -> bool:
     if not (env.PROXY_BYPASS_PRIVATE or env.PROXY_BYPASS_DOMAINS):