There was just a big debate on the forum about this exact thing. From what I understand, the E53's system is just as crappy as the E39's. There appeared to be two camps, 1) replace it all at once, 2) replace stuff as it fails.

Really it comes down to your preference. I'd check the other components but would probably just replace the hoses for now.

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03 3.0i mt
89 325is