2 month sets was definitely later. we didnt have 2 month sets until EC i believe which started in either late 2006 or early 2007.

postedit:
actually scratch that. it may have started in 2005 when there were changes to ghost acres (they were removed). the thing to realize is that it probably occurred with some other changes when mehul was definitely running earth and so he would do his once every 99999 year update. i am 90% positive it was 2005 with the ghost acres change