Auto-Enable also enables expiration when editing existing posts

We have set Auto-Enable? (‘Select whether the post expirator is enabled for all new posts’) to Enabled. Default expiry is replace category by category ‘Expired’. This is very handy because over 50% of our posts are announcements of one-time events and other posts with a temporary validity.

Recently I noticed that this also enables expiration when editing older posts that date from before we installed this plugin. From the documentation I cannot make sense of whether this is by design. This is in our case very undesirable behavior.

We have several large archive categories with contents that remains valid for 10 years or more. An assistant editor is regularly reviewing those and fixes broken links and styling.

Is there a way of keeping it auto-enabled for only new posts but not for editing existing posts? Or limit it to a certain category e.g. ‘News’?

The page I need help with: [log in to see the link]