I would have to disagree on all of this presoften business, sorry guys and gals. And by the way, Rivendell agrees with me.

I have a Brooks Swift TI saddle and I did not use anything to hasten the breakin period, not even the Brooks recommended Proofide. Did it take longer to break in? yes, about 500 to 700 miles, that was roughly 4 weeks. But presoftening the leather will make the leather age faster thus the need for using the tension spanner sooner and more often because the leather will sag as Roadbuzz pointed out. But my last Brooks was a B17 and that saddle never needed an adjustment, unlike what Roadbuzz had to do; and that saddle also never had presofteners applied. A leather saddle is not much different than leather shoes, but we don't apply presofteners to our shoes and they eventually break in, so why would we do this to our saddles? Because we want the saddle broken in now but at the cost of durablity.

You can use water proof treatments (the kind for leather hiking shoes) to prevent water damage to the leather if you sweat a lot or ride in the rain; or you can buy a seat bonnet that will protect the saddle from the water.