Two main points: 1. Brooks saddles vary a great deal. 2. So do the riders.
How do Brooks saddles vary?
1. They offer many different models, with different frames, different rivet choices, different leather treatments...
2. Despite all their experience, the do not have complete control over the leather they buy and make into saddles. They get it from a tannery that prepares it to their specifications, but every piece of leather is the hide of an animal, and neither Brooks nor the tannery has complete control over that animal's life. They know what they're doing, and it's not a crapshoot, but they don't have complete control.
3. When we talk about Brooks saddles, we lump saddles made last year together with saddles made in the 1970's or earlier. The leather used in 1970 was different from the leather used today, and the leather used in the 1970's is now 40 years old. These things make a difference.
4. Brooks models have changed over the years as well. B.17 was once the top of the line; now it's the standard product. And so on.
5. Aside from the above, some of us opine that Brooks has intentionally changed the way they make saddles, so they are now intended to be comfortable from day one, at the cost of longevity; in contrast, fifty years ago they were intended to last pretty much for ever. I believe this is true, but I'm not certain.
How do the riders vary? Reread this thread. @
cyccommute won't ride without padded shorts. I won't ride with them. No big deal for me; I pretty much always wear cotton briefs and cotton shorts. My mileage for the year is over 4000, including a dozen rides of over 100 miles and two of 200 miles. No saddle sores. @
winston63 finds the reference to "divots" puzzling, but I don't. This is doubtless related to the fact that I ride in cotton, which can get wet as I sweat. On a hot day my saddles often start to get a little wet, and when leather is wet, it softens. My saddles always develop indentations under my sit bones; and they usually get a little asymmetrical (always in the same way). By disagreeing with these forum members, I don't mean to say they're wrong; but evidently they ride differently from me and as a consequence they experience leather saddles in a different way as well.
It is true that water doesn't really do that much damage. But riding a soaking wet saddle can seriously stretch it out, and whether you call it damage or not, cannot be undone. Similarly, repeated soaking, even without riding, will wash soluble materials out of the leather, and as this happens, the leather changes. It gets harder, less resilient, and it shrinks. Again, these changes cannot be undone.