For years and years I wore leather boots and did my best to take very good care of them. I tried all sorts of oils and silicone treatment, mink oil, bees wax, Sno-Seal, you name it I tried it. I found that I didn't like Sno-Seal very much because too much of it stayed on the surface and cracked when cold. Most of what I tried just didn't work well. Then I found Limmer Boot Grease from Limmer Boots, the custom boot maker in the States. I once ordered a pair of off-the-shelf Limmer Boots (as opposed to their custom boots, which at the time was a three-year wait) and ordered some of their boot grease along with them. The boots didn't fit well and I sent them back, but I fell in love with the grease. It worked well into the leather just by the warmth of your fingers, it protected well and lasted a long time, it never cracked or settled on the surface, and it kept the boots very water resistant while at the same time keeping the leather reasonably supple. I've not found anything better.
Though I rarely wear boots anymore I miss them. I like the durability they have and the maintainable nature of a product meant to last for many years. Until I got into UL and started going through ridiculous numbers of trail running shoes I had one pair of boots that I still own today... a pair of Merrell Wilderness boots that I bought in 1988. I've resoled them twice, but the uppers are still perfectly fine. I've thrown away lots of shoes, but these I will keep for as long as I can, in spite of their weight.