Technically, the spider breaking in
does happen, and would change bass frequency response / tuning, but nothing worth waiting for. Nothing like "Before it had no bass, and now it does". More like "before it had 110db of bass output, now it only has 109.5db but goes 2-3hz deeper
It's definitely there, perhaps even audible if did a side by side comparision with the right content material. But I don't think a person could tell the difference after actually waiting for break-in. The time in between would be great enough to change perception and create confusion.