sed s/\ /\\\n/g < Ask_YC_Archive | grep id\= | cut -d '=' -f 3 | cut -d '"' -f 1 | sort -n

gives 363096 as the highest id there, so http://news.ycombinator.com/item?id=363096 is the latest entry that was added to the collection, which is 1 year and 9 months old.

There must be plenty of quality stuff added in the meantime. Is there a reason why the list is no longer updated? It's a wonderful resource by the looks of it.