dropped table modified date older than 45 days

 Hi All,

I got a request from my customer, they want me to drop some tables modified date older than 45 days. I have searched all information from metalink and google, what I got just use dba_tab_modifications or user_tab_modification, but those two views just can provide 5 days information. If the modification information old than 5 days, I can't get anything. If any way I can  do this work?

Thanks a lot,

kelvin