It is said that you remember 10% of what you read (more when hearing is involved and even more if you both read and hear).
10% is not much. You can be fairly certain that your readers do not remember what you said a year ago.
Furthermore, since last time you covered a topic you will probably have had lots of other experiences that could deepen the topic or even expand it with another topic branch.
Everything you say is true @ronni.
As much as anything... in worrying about whether a potential reader might be "bored" because I am repeating myself, I also have to ask myself the question whether it is me who's getting a little bored with what I feel like might be "the same thing."
Things change every day... and my perspective tomorrow will automatically be a little different from today.