If I remember correctly the Archives section was introduced mainly to make the site run more efficiently, there is less need to have it these days and there has been talk of merging Teens and Archives into one new section for some time. It is not really meant to be a section for retired or more popular models, it is somewhat outdated really.
Titles also are slightly confusing, Teens is really for any model who is not a milf. There can be grey areas when you are not really sure which section a new girl should go in.