I agree, the public tends to move from atrocity to atrocity, and unfortunately, there is always another one right around the corner. But all these years later, there is still plenty of information online about the Laci Peterson case that was originally published back when it all happened.
A lot of what can be found likely depends on the amount of public attention given to the case, and how many media outlets were reporting on it. In the Watts case, I think it has all of the elements to be every bit as large as the Laci Peterson case, and perhaps ever larger, before all is said and done. If you type in the right combination of words into google, websleuths posts are already showing up on this case.
I'm not sure how long these posts will remain in the search engines online, but I think as long as people keep posting on it, much can be found with the right words and the right search engine.