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Whats wrong with the natural oils of the hide as well as the tanning oils already present in the leather?

It will start to stiffen, this takes a long time to happen and I wouldnt think it would be an issue right now, unless of course it is in direct sunlight or is subjected to some other heat source.

If its new I would think that this is not necessary, but in time as the leather starts to dry out it will become necessary. Try it as is.