i read all the books and i think tat after it was revealed i think it was closed shut and destroyed or it closed down 4 ever cuz the heir of slytherin was revealed...
I think no one bothers with it after the Chamber of Secrets. But Ron and Harmionie go down there in the final book to get the basiliek's fangs to destroy the Horocruxs.
It might not be secret anymore but it is still impossible to access unless you know the correct word in parsel tounge. So basicly it's shut closed, unaccessable for almost everybody.
Its not exactly shut down but you need to speak in parsel tongue to open it so no one can get in, however Hermione and Ron get in to in the last book because Ron repeats what Harry said to open the locket.
