I have to do a lot of public speaking and briefing/presenting with my job. I barely stutter during either event. I've noticed the older I get (nearing 30), the less it happens during certain circumstances. I imagine that Biden is in a similar position. However, it's weird sometimes. I can now go a couple of days without stuttering once. And then I'll have a bad day where it's literally every few words and I just limit my talking that day haha. I've definitely noticed that when "the pressure is on", it's nonexistent. That's something I've had to develop over time. I also noticed a significant change when I just developed a "yeah, I'm going to stutter, I don't give a shit about it and what you think" kind of attitude. Ironically, that attidude has made me stutter less than normal due to confidence, etc.