Disable comments on old posts in WordPress

You can prevent users from commenting on old WordPress pages and posts as a way to help prevent comment spam.

Log in to WordPress
Go to Settings >Discussion
Locate the Other comment settings section
Check the box next to the line stating, "Automatically close comments on articles older than XX days"
On the same line, change the Day setting to the number you prefer
Scroll to the bottom of the page, and click Save Changes.
After making the above changes, users will not be able to comment on any pages or posts after the number of days you specified.

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