Thanks for the response. Been a while since I remembered making this post and came to check. 😄
To answer, no.
You can only delay a post lock by editing the opening post or when making a new thread. You can't do it on a reply or by using the moderator action button, because you don't get the full administrative/moderator options on a reply to a thread.
I don't want to do that (mostly because the main type of deal I want to use a delay lock are news articles with a forum thread that generate automatically from a database entry and I really don't want to mess with these automatic OP posts.
I want to make a post in a thread and be able to set a delay lock, with a notification in the new post (although a notification isn't quite necessary as I could just say "it will lock in xyz minutes").
Also, it wouldn't help if they try to post a reply after the lock has gone through, so I would want to add some kind of post-lock attempt to post page that gives a person the opportunity to save their post or copy it. Sort of like how if you try to edit a wikipedia page, but someone else has pushed an edit to the page before you, it gives you an edit conflict page with a copy of what you tried to post.
And/Alternatively, there could be an option somewhere to simply allow posts to be made by anyone with permissions, within a certain amount of time of a post being locked.
Thanks.
Notes: Lock options for a new thread or editing OP:
What shows when using the "Lock Thread" option in a thread: