Slide titles should be unique. Every slide in the slide deck should have a purposeful name. It’s easy to use duplicate titles but do your best to avoid duplicates.
Slide titles are easy to manage if using an accessible slide theme.
How to apply slide titles in PowerPoint Video Overview

Why should I have unique slide titles?
People who rely on assistive technology to review presentations will often navigate by the heading or title structure. If you end up converting the document to another format like PDF, the slide titles will come through as headings.
Failing Example
In the example below there are 5 different slides that share the exact same title.

Passing Example
In order to apply unique slide titles simply add a number to the end of each slide. The quickest method to change the title of a slide is to edit in outline view.
- Select View
- Select Outline View

Then simply add a number or change the title altogether. The image below shows an outline view of a presentation with numbers added to make slide titles independent.

Note
The built-in accessibility checker within PowerPoint is exceptional at notifying of this error. Would you rather hide the slide titles?

