Lessons from Teacher Ciruela
I already said that!

Some colleagues of mine get very annoyed at having to repeat explanations or answers more than once. Maybe they don't realize that learning by repetition provides a solid foundation for gaining knowledge. You can't expect to learn something in a flash only because you've been told once. Fresh ideas have to fight their way through countless causal relations that have already been fixed in our minds. New thinking processes can only be grasped and set by means of taking repeated shots at strengthening newly created relations, back and forth, going over the reasoning path again and again.

On the other hand, some other colleagues (not many, though) are well aware of the need and the importance of repetition in the learning process so they would willingly answer for a second time... but would not even mention the fact that they had already done so before. Even if they fully and naturally embrace the idea of repetition, they still feel rather embarrassed at leaving the clingy student in an offside position for having asked the same thing for the umpteenth time. I'm sorry to say that these teachers are also wrong: stating "I've already explained that" is a healthy thing to do. It helps the student reset the whole issue. The second time you listen to something being told is always quite different from the first. The second one becomes pretty enhanced as it taps into some more relations, consequences and nuances than those mentioned earlier about the same concept. This second time would aid them in plucking that previous chat from obscurity. Maybe it's just that: becoming aware that they had already asked the same thing before leads them to finally get it.

When we tell an absent-minded student that this matter has already been dealt with, then we are helping them call to mind that former elucidation that will enrich the present one. If endowed with expository skills, the teacher will wisely make the most of the situation in which answers happen to get reiterated.

Finally, my dear colleague, the student that insists on this annoying habit has a very good chance of sizing up your revenge at the time of the final exam, for not having paid enough attention every time you opened your illustrious mouth. To the ones lost in thought, there goes my advice: be on your guard! Being prepared for the unexpected is no small feat.