Opus already acknowledges that some people may want updated results for a Windows Search query, which is why it has the "Refresh Results Automatically" for the Stored Queries.
Instead of waiting for the user to visit each one of the stored queries, why not have a way to notify him whenever anything new is found?
This could be accomplished if Opus could return an feed (RSS/Atom) of the results of a query - which the user would then use in his feed reader.
Now that it has an http server built-in (for the help), I guess it should only need to convert the collection representation to a feed representation.
There is at least one desktop search engines out there that can output a feed, but then you have to double the effort with indexing your files again, and it doesn't support as many formats as Windows Search does.
A solution can probably be made by asking opusrt.exe to run a query, then export the collection, then construct a simple feed based on that, probably with only the file paths.
A built-in solution could probably output a feed much more rich, with multiple metadata fields, similar to the tooltip, and maybe even text snippets (like Explorer shows based on preview handlers).