I am a big fan of Brooks Saddles, and have 3 bikes with B-17 saddles on them. Saddle #1 was bought about 10 years ago, and is on a bike with ~13,000 miles on it. This saddle seems to have a thinner leather than the other two, and is considerably softer. It has also been abused more than the other two, having been ridden in more bad weather etc. Saddle #2 was bought about 8 years ago, and has ~5,000 miles on it, and looks almost like new. Saddle #3 is on my daily commuter, it is 4 years old, and has 9500 miles on it. Although comfortable, it looks hardly worn at all, and might as well be new.
I don't regret purchasing any of the three saddles, I do wonder about the oldest of the three if it's wear is a result of a bad manufacturing batch, or my mistreatment of the saddle, but I can't seriously complain about a saddle that has only lasted 13,000 miles.
Where I find the greatest value in the Brooks saddles is in long rides. I have ridden on a Brooks from Montreal to Boston with no pains in the rear - and that makes it worth the cost, even if it had only lasted for the one ride!