Re: It's getting annoying..
Michael, others have said harsher things than you have.
A sempai is the more advanced of two students - no more, no less. We all have sempai, those who started training before us/are more advanced, and kohai - those who started training after us/are less advaned. Someone who always is training with his juniors will be in the role of sempai all the time. When he's training with seniors or with people his own level, obviously he doesn't have to be doing any kind of mentoring/teaching. Then he can relax that part, and concentrate on other things.
I do think the Japanese stresses this more than Westerners typically do. But when you put advanced students to train with beginners, surely you are asking of them to act as sempai.