In Meridian Portal, users are given the flexibility to set/define the "Due Date" before send the document/package.
However, there isn't any email notification been triggered/sent to users to remind them on the task that still pending their response and indicate the due date of the documents (perhaps x days before the expiration - can make this setting configurable).
It will make the process complete if the system is capable to automatically sent an email notification if the user has still not working on the assigned task at x number of days (or x days before the due date), at least users are aware/alert with the assigned tasks.
Others things to consider, what will happened if the task reached the due date? Can user still open and working on the task? Or there is a status indicated the task is expired and user are not able to work on the task again until the original user who sent the document open and reset the due date?