Do repeat yourself
It's Ok to repeat yourself. You've likely heard this before. You might have heard this so many times that you're tired of hearing it again. If not, then congratulations you're about to read something new. Otherwise, time to chose whether to read on or not.
The Importance of Repetition
Repeating is important. For the "repeater," it's about consolidating and organizing the message. Our opinions change over time, sometimes faster than we think. There's a chance that what you believed in, even if it's something technical, might not resonate with you anymore as you learn about other relevant topics.
Most people need to actively "visit" a thought to check it; saying it aloud or writing it down is a good way to do that. Saying it aloud to someone else has the added benefit of seeing and hearing their reaction. You might either help someone learn something new, or you might hear feedback that will help you validate your thought. It's a win-win situation, provided you're both civil about it.
Why we avoid repeating ourselves
One of the most common reasons why people avoid repeating themselves is because they don't like to repeat themselves, and they don't like to hear something they already know again. Yes, let me repeat that: I believe we avoid repeating ourselves because we don't like to repeat.
We might think, "Why tell something again and again? It's a waste of time. Shouldn't they already know this? I mentioned this at some point." Reading this sentence might make the problem quite clear, but, thematically, let me repeat the conclusion: they aren't you. There are many reasons why they might not have heard this; for one, weren't around when you said it, or they contemplated on the previous point, or there was an explosion nearby and they didn't hear it. So, it's less about you and more about them. Sorry.
Dealing with repetition-averse listeners
Lastly, and perhaps the most difficult part: what if you're sharing something with someone who has heard this before and doesn't like hearing things again? This is indeed a problem. I usually explain that I didn't have bad intentions. I add that I prefer to err on the side of over-explaining and risk being perceived as annoying, rather than implicitly expecting them to know everything and closing doors in case they don't.
Basically, I'd rather waste 10 seconds now than leave awkwardness that lasts much longer. If they don't like to listen, they might not want to listen to you in the first place. And if they are ok with listening... maybe repeat this internet message to them?