The Brooks stuff will work, and if you apply the amount they recommend, and at the suggested interval, that little tin will probably last you 20 years.

I only put enough Proofide on to protect against the occasional drops of rain that make it past my butt. I cover the saddle (one of mine came with the fancy Brooks cover; a plastic bag would be enough, too) if I expect it to get rained on. If you like how it feels now, don't do much of anything to it.