Hi Jos,

This is a really interesting question.  If this is something you still haven't found a solution for, you may want to submit an enhancement request.

I think you have a couple of options.  If your process is such that the date the request goes into the submitted state is the same as the creation date, you could create a query that checks creation date is greater than 25 days ago and status is Submitted.  You could have a dashboard that shows these queries for each product owner.  It's not email notification, but it would give you some sort of reporting.

If the creation date is not the same as the date the request goes into the submitted state, you could add a custom attribute that records the timestamp of when the work item goes into the submitted state.  https://jazz.net/forum/questions/68205/how-to-get-modified-date-attribute-of-a-work-item has a discussion on this idea.  Then you could create a query as described above.

Another option that might work is to write a custom script that checks the work item's history via the api to see if any of the work items meet your criteria.  https://jazz.net/forum/questions/884/extracting-workitem-history has a discussion on this idea.