I managed to do a search from 2 months old to less than 5 years old and I searched on aiko. It brought me up three pages of results - which doesn't seem very much for such a popular character so I guess it all depends on how efficient people are at putting in key words. Its seems a very tedious way of doing things though :(  if the only other way is to look at a complete month by going to the archives. The other thing I noticed is that it wouldn't let you select things at the right hand side and not put a search word in at the left hand side. By the way category is spelt incorrectly at the right hand side as well.