In the style of Yakov Smirnoff, it would seem that you don’t break in a Brooks Saddle, it breaks you in. This is probably a bit of an exaggeration, but after my first proper ride on my new B67 saddle, it feels as comfortable as my older B66. It is probable that a small amount of breaking in occurs, but most of the changes seem to be in the rider’s arse.
Brooks saddles are like many luxury items, once you have one, it becomes more of an essential than a luxury. Think back to life before your first mobile phone, you managed fine without one, but now it feels like an essential item. A Brooks is the same. I wholeheartedly recommend the B66 based saddles for upright bicycles, but just be aware that once the saddle has broken you in, other saddles may feel like crap.
The B67 is almost identical to the B66, differing only in that it is compatible with micro-adjust seatposts. Having a B67 saddle on the Yuba makes it much more pleasant to ride, plus I prefer to have the same saddle on the bikes I use regularly (providing they have similar riding positions).
My test ride was along the Fallowfield Loop, in the fog and later fog and rain. It was still quite an enjoyable ride, the dynamo light illuminated the fog creating the sensation of riding through an over-exposed photograph. When the rain picked up, it gave me a chance to test out the rain-worthiness of the bottle dynamo. Re-assuringly there was minimal slippage (if any) and the light stayed perfectly bright throughout the rain. The increased temperature also meant that I didn’t have the same gear problems which the Yuba suffered from on Xmas day.
If you have a Brooks saddle and have been considering investing in another one for a second bike, but have been worried about going through the break-in again, don’t worry. Your new saddle will feel almost completely broken in from the start, because you already have been.