I feel a lot more comfortable in jackets that are "experienced" .. so every now and again I find myself with one with a damaged top coat or rot. In the past I've used rubber cement then dye to delay the inevitable deterioration and make a jacket more wearable. (jacket's still going to be around longer than I is) .. turns out this is what Dena will do as well. Anyway, lately I've been using this stuff that book restorer's use on antique leather bindings called Klucel-G, it's described as a "leather consolidant" (is that a real word?). It's a lot less viscous than say rubber cement so it penetrates the exposed or rotted leather more deeply and after it dries it stays flexible and leaves the area no longer turning to dust and more solid. So far in my experience it works fine and hasn't darkened any jackets at all. YMMV obviously.