the reason i advice to buy new brooks saddle is that you might need to use their warranty offer. many audax riders agree that the leather of new (i.e. after the company was bought by italians) brooks saddles is thinner/softer and goes out of shape quicker, which usually is not a good thing. i've had to return my b17 after very wet lel'09; it collapsed in five days of riding in the rain. brooks kindly replaced the top with a sturdier leather and it's been fine so far.
Interesting that you mentioned about the saddle collapsing after LEL. I experience pretty much the same after a wet tour in NW Scotland, despite all my efforts to keep it dry when not riding on it. When I got home I noticed that the leather was very saggy. Got in touch with Brooks and they said I should let it dry and then re-tension it with the bolt. It's now back to normal, although it's shape has changed quite a bit. I wonder how many more of these wet rides it will take given that the tensioning-bolt is now 1/4 of the way used?