If you need to. Sometimes a project goes into a kind of cruise mode where all you have is a string of Next Actions in a row that can only be done one by one, and the mindmap isn't needed.
Other times though a project might suddenly go off on five directions at once, and the mindmap is vital to make sure you don't forget any of them.
So you don't have to look at it every single week, but its probably an idea to have them to hand.