It doesnt particularly seem as if new threads are harder to find than old ones. I have tried looking for threads several years old: some it finds, some it doesnt.
Very very new threads it doesnt find, but that is different It generally finds most new things in a day or two. But then it sometimes seems to forget them. And I cant help feeling the explanation lies more in Mudcat than in google, but I dont understand what's going on to really come up with a theory.