A long conversation is just a bunch of short conversations. Try to look at it that way. I feel like the biggest problem with my stutter is avoidance. I have to keep on my self not to avoid talking. My stutter is directly tied to my anxiety so if I avoid pushing through with conversations it's just harder next time. The more I find I push through when I don't want to talk the more confident and less anxiiu I am to push through the next time and being less anxious makes my stutter improve.