Estimating historical read time for a large forum import

I think I’d do something like

Post.where(user_id: user.id).where(some other stuff?).each do |post|
  PostTiming.create(topic_id: post.topic_id, post_number: post.post_number, user_id: user.id, msecs: READ_TIME_MSECS
end

If I’m doing the arithmetic right, 300 seconds is 5 minutes. Do you think that it took 5 minutes to read and respond to this post?