Average adult attention span is 8 seconds…………..
…so I just about still have you….
That is one estimate.
The other is 20 minutes. Probably more reasonable, less attention grabbing than “You have the attention span of a goldfish”.
You must be able to hold attention for however long is needed. Woeful Powerpoint presentations running to 40 slides of wordy drivel and non-impactful stories, images. Completely forgettable.
That will make you unmemorable. The audience will leave physically before you are finished, and in their own minds they will have left the what you do and how you might help far behind when the screen closes.