Studying the classics helps us to learn chess ideas ("chunks") that we can put away in our long-term memory, but we can also benefit from material we look at just before a game, too. By reviewing familiar ideas, we're primed to spot them when they come up in our games.
Witness illustrations of both points, here. As always, the show is free (free registration is required), and will remain available on-demand for the next month or so.