Unless a family member has access to it (you must not only givethe person a key, but must also sign a form at the bank authorizing that designee to open it), the box could be sealed when you die, and it might take court action by your heirs to get it opened.
The ruling Thursday undoes a 2008 trial court decision ordering Warner Bros. to share an undetermined amount of money earned since 1999 with the heirs, and to givethe family control of key components of the Superman story, including his costume.