Some might be surprised how old mapping data is for even regularly-frequested parts of the globe. I make a habit of reading the Hydrographic info printed on the chart whenever I open one - it makes for an interesting history lesson sometimes!
On rare occasions, people have been known to change the topography enough that known mapping data is no longer correct. Examples: A certain property developer in the Whitsundays caused some excitement a few years ago during construction of his multi-million$ resort and I'm told it is amost impossible to obtain an accuarate chart of Singapore or Dubai without getting a subscription on a weekly basis..
