If you see them again, it is definitely worth asking them what they want, or if they have a message for you. You could try telling them that this is your dream space, and they are not allowed to hurt you or trespass without permission. I am interested in hearing what their response is. I think that it is strange that they have maintained a presence for so many years. I may occasionally have a reoccurring theme for a year or a couple of years, but not usually longer than that.

Just as a side note...what is the lucid dreaming audio that you were listening to?