I've been using oil on my hunt seat for the whole 15 years that I've had it and it looks pretty much new still, it really hasn't deteriorated at all. not that I am saying you are wrong, just that was how I was taught to clean/condition saddles.
I hated the color of my saddle (oakbark, yick) and I was able to darken it with simple olive oil (my trainer when I was young swore by olive oil for saddles). You just heat up the olive oil and then rub it in with a thick towel, being careful not to touch he hot oil. My once Oakbark saddle now looks brown. When I brought it to my current trainers that I am using for Cinny she thought it was a near new saddle lol.