To what point do you stop re-making movies.

If I had read The Glass key and then seen Yojimbo and was not in a film class I admit I would not see that they were related to each other.  However since I am, and have found out that Yojimbo, Miller’s Crossing and even Fistful of Dollars are all remakes it makes me think, to what point do you stop redoing them. Though Fistful of Dollars is a nostalgic film, Yojimbo mytologizes it, and Miller’s Crossing is the newest interpretation, for a student that is forced to see the differences, it gets to be a bit much eventually.