I’m a speech therapist with a stutter, I’ve utilized DAF in research as well as with clients so I got ya. You’ve found an AMAZING tool that helps in limited opportunities for a limited time. People who find out about DAF and then use it 24/7 quickly normalize their brains to it and lose the benefit. As for using it for a presentation, there’s absolutely nothing wrong with using tools to help you. Whether it’s reflected in your performance or just your comfort, you deserve to be experience life as not just a “stutterer” and if wearing earbuds does that for you, do it. Warnings though, aforementioned lack of continued effect means that you have X amount of hours using DAF before it doesn’t work anymore, I think high stress presentations would be a good use of those hours and you shouldn’t worry too much. Plus, being confident you won’t stutter makes you not stutter. Not just from a mindset perspective, but a neurological one. So if it makes you feel better then do it!