If it were my saddle, I'd put it out in the sun, or in a pinch, in an oven warmed to 120 degrees or so. Oil "dries" through a process of oxidation, and elevated temperatures will speed this up. Getting to warm will damage the leather, though - 120 should be plenty safe (no worse than leaving it in the sun for a bit), but much warmer and you'll really be pushing it.

I wholeheartedly disagree with Sheldon's advice for soaking saddles in Neetsfoot oil - to be fair, I haven't done it, but it seems to me to be a perfectly good way to ruin several pairs of pants as the oil wicks out of the leather. If I didn't use Proofide on mine, I'd be tempted to use Sno-Seal, which like what others have talked about is mostly beeswax. That's what I've used on hiking boots for years, and while I've worn out several pairs of boots, it's never been the leather that's let go.

My B-17 has no noticeable give under my 250 lb. Clydesdale weight after two years and 5k+ miles, but it's still a rather comfortable saddle for me. If the basic shape of a Brooks doesn't fit your posterior, I suppose that puts you in a bit of a pickle if it doesn't break in all that well.