Adding a new block for each announcement can give you as many announcement bars as you want. In addition, you can set the announcement bar to appear periodically based on the Show again after option.
Show again after
The Announcement bars always appear in the admin view for design purposes.
This option allows you to set a specific time for the announcement bar to appear again after it was closed by the user. Of course, for the announcement to disappear, the user has to close it first. If the announcement bar I not closed or the close button is not enabled, the announcement shows at all times.
This feature uses the user's browser cookies to remember when they closed the announcement bar and show it to them again after a period of time.