If you have a dashboard that needs to be copied in the future, so you can create new dashboards based on that one, it's a good idea to set them as a template.
It is useful to have dashboard templates if you have for example a standard method of analyzing the status of a project. In this case, it would come in really handy to have the possibility of using the same type of tracker to many boards.
This is done with the option on the dashboard page, when you click "Dashboard details", under "Edit details".
Then, enable the use dashboard as templete option.
The next time you create a new dashboard, you may select "copy a template" and select the dashboard that was set as a template.