I have a team pro from the early 80's which has at least 30,000 miles on it. The bottom is neatsfooted and the top has been treated regularly with saddle soap. Never has it seen proofhide until this year. It's a touch hammocky, but very comfortable on our tandem. The surface of the leather back by the rear rivets is a bit cracked, but it's still hanging in there.
I have a new team pro. and my wife has a b67 and a flyer S. We are treating these only with proofhide. Ask me in another 25 years and another 30K miles and I'll have some data.
I neatsfooted the bottom of my brooks to protect it from the rain. I proofhided the bottoms of the new ones for the same reason. You guys who don't treat your saddles or only sparingly so, what do you do about riding in rain? I never go out in the rain, but I get caught more than I'd like.
Sheldon