As part of Deskpro's 2019.4 Release, there is a new feature that will allow you to place a limit on how much time Users have to re-open a ticket. This feature allows you much more control over the behaviour of your users. Instead of simply granting or removing the ability to re-open a resolved ticket, you can decide what an appropriate amount of time is for the user to re-open the ticket. As this is set with the permissions of a User Group, you can allow different time frames depending on the type of user.
To set this time limit, head to Admin > CRM > User Interface > Permissions. There are a number of time frames to select, ranging from 1 day to forever.