I do it from time to time, depending on the situation, in order to have more chance to follow and thus to keep participating in a conversation with my full attention. If I'm preparing something to say as response or comment on the current subject, I build up the answer in my head, seaking the words which are more easy to say for me as an stutterer, I'm occupied with that sentense (response)I untill I actually can say it and takes alot of my concentration and some times I need to just say my sentence so I can follow the conversation again, and still give a contribution, my vision in short, I do this to be able to continue following the conversation.