How to set due date/expiration date to observation checklist notifications.

Summary:

How to set due date/expiration date to observation checklist notifications (Bpm workflow notifications). And also can we set it for 60 days.
According to the document ,that says " No matter what the task status is, the scheduled process also removes notifications that are older than 30 days from the notifications list, Things to Finish section, and Notifications page".
-Synchronize Notifications in the Global Header and Home Page with Workflow Tasks

So is it possible to set the expiration date for the notifications to 60 days. Please help us with the steps to implement that

Thanks

Content (please ensure you mask any confidential information):