Why do you think Facebook will still exist by the time you die? If you want to keep your data for an extended period of time, it would probably be better to do it yourself.

You can download all of your data from facebook now. It's a link at the bottom of your account settings. Only thing of importance missing is your comments you left on other's status updates. To think if Facebook bit the dust that someone else wouldn't do something with that data is almost unthinkable at this point.