My understanding was that only posts in Explicit get automatically deleted, but I can't find some of my posts in the Science & Skepticism section.
After podcast #290, I went looking for a reply that I wrote a few years ago on the value of animal testing. I remember it as being really good. I pointed out that vivisection enabled the discovery of insulin, that the DNA evidence shows that animal models can be 99% identical to humans, etc. I was gentle and even-handed to the anti-vivisection proponent. Unfortunately, I now can't find that post anywhere - not using the forum search tool, not using Google.
I don't think it's an age thing, because I can see other posts I wrote as far back as 2006.