How do you know whether to trade one of the rook pairs in an endgame? I've been reading Endgame Strategy. I've seen, in a lot of the games, trading one of the rook pairs can help. There is a chapter in the book called the 'Problem with Exchanging.' I don't know how to determine when trading one of the rooks is beneficial for me.
One question to ask is "am I behind or ahead?"  If I have some winning edge, it's best to simplify.  If I'm behind, it's better to complicate the position.

After that, the question has both tactical and positional elements.  If my rook is less active then my opponent's, it's better to exchange.  If my rook is more active, then it's better to keep it.