You mention oiling.

Various types of oils can migrate down the leather and eliminate the bond between leather and sole. Over-oiling, or forcibly injecting oil between the leather and sole should be avoided.

I might add, I am very careful about oiling vulkanized, bonded boots. The old double welt and Norwegian welt soling systems are theoretically and probably in fact tougher but some of the bonded boots hold up very well as we all know. I prefer the types with a synthetic sealant added during the currying process to waterproof the boot.

My ski-boots have now seen some years of use in really bad conditions for a boot, with many hundreds of miles under them both on skis and on snowshoes and just on the ground {they are a hiking boot as well}, they holding up very well tho I've had to make a few stitching repairs, stitching sealed with Shoe-Goo. No delam problems and these are used in water and mud constantly.

My recommendation for bonded boots is to allow the factory waterproofing to protect the boot as long as possible, and then, find the wear spots and then rub the wear spots with acetone and after drying, rub a thin coat of Shoe-Goo on the spots. Looks like heck but works.

DO NOT APPLY OIL TO A BONDED BOOT/SOLE SEAM OR INTERFACE!

I am using a couple new boots this year, one a pair of Merrells "corked" by Hoffman Boots in Kellog, Idaho. The caulking process involves the grinding smooth of the factory sole, application of a new flat sole with the caulks installed. We'll see how it holds up. The loggers love them, except they don't meet safety standards for industrial wear due to their low 6-inch height.

I'm also using a pair of Asolo boots I got not long ago. They have Gore-Tex {unlike my White's} and after a hundred miles on them they are doing well.

All of the above; Merrell, Asolo and my Salomon ski boots are bonded boots.