Game extras

Do you try to accomplish all the extra bits and collect all the extra items your first time around, or save that for a replay? Do you play any unlocked features once you're done? Assume this question is for a game that's good enough to have replay value, because the answer is obvious for bad games.
I save the extras for replay. Usually. And, playing unlockable features? Depends on the game. I've played Mercenaries in RE4 to death (probably more than I've played the main game), but on some games, only the main content is replayable.
I save the extras for replay. Usually. And, playing unlockable features? Depends on the game. I've played Mercenaries in RE4 to death (probably more than I've played the main game), but on some games, only the main content is replayable.