It's important to know the very basics, i.e. how to checkmate with all the different pieces, how to calculate simple King and pawn positions, etc.
Endgame study can be turned into tactical puzzles; they are often times the same thing. Tactical puzzles can be taken from any part of the game. It's important to solve endgame tactical puzzles and know the basics otherwise you'll blow some games in an embarrassing fashion, i.e. blowing a two pawn lead, or losing when you're up a Knight, etc. because you don't know how to close out games in which you earned a winning position through superior tactics.
Endgame knowledge is the first thing someone should study in chess I think. A good knowledge of endgames helps shape your middlegame, which in turn helps shape your opening. Knowing what you are looking for in an endgame makes middlegame decisions much easier.
Much like in golf... it's "drive for show, putt for dough". It's the finishing touch which makes the biggest difference in your performance.
that was full of truth.