I don't really use proofide to waterproof my saddle. I apply a tiny bit of proofide maybe once a year, but that's about it.

I don't leave my bicycle out in the rain very often. If I do, a plastic grocery bag or shower cap goes over the saddle. And otherwise my butt (and rain jacket) cover the saddle.

Some of my bicycles have mudguards, and some don't. The bicycle which had the Brooks with 45,000 km on it had mudguards about 1/2 the time, and I rode that saddle in all sorts of weather from blazing sunshine, to bucketing torrential rain, to sleet and snow. The saddle was fine. In fact, it was, by far, the most comfortable saddle I've ever owned.


Edit: Even when I did not have mudguards, I did ride with a rack with a flat top piece so it would have sort of helped act like a mudguard to some extent.