We have a user task with the three following options: Save Work, Approve, and Reject. 

When the users want to update the form without continuing onto the next task, they can select the "Save Work" button and route the instance back to itself.

The users can take up to a month before approving the form onto the next task. 

For example, the user saved the form once it was assigned to them. The task was assigned to that same user for up to 20 days. When the user updated the form, they wanted to save their work instead of approving the form. When the user attempts to save their work a second time after the 20 days waiting period, they are unable to save the form. They must reassign the form to another user and allow that user to finalize the form.

I am receiving an error within the event viewer stating that the form pages expire. Like I said above, this requires the administrator to reassign the task to another user in order for them to move the form onto the next task.

How long can a user task be assigned to a user before expiring? 

Should I set a timer event and automatically reassign the task to itself before it hits the expiration deadline? 

We do not want the "Save Draft" feature, which does allow the users to save their work. However, they don't want to use that feature because the draft cannot be viewed by other users that didn't save the form.