I did one at end of bachelors, end of masters and now frequently during my PhD. People know I stutter but it isn't that bad in general (have bad days though). For my bachelor's I didn't mention it to anyone. Everyone only had 10 mins else you lost marks for running over. Obviously this time pressure was terrible and really affected me. After that was one of lowest I ever felt. Fast forward a year I had a 15 minutes end of masters talk, however this time I told the lecturers before. This time pressure relaxation meant I was more fluent and actually didn't even need the extra time. Now in my PhD talks I will openly say I have a stammer, as it kinda relaxes me. Have employed this at interviews and stuff too. People appreciate the bravery/honesty I think. Since you are covert, people may think your stammering is just down to nerves rather than a condition, which may be preferable to some people possibly.