Pinion seal leaking, dealer recommends not to replace
I have a 07 335i that I just purchased the CPO has a couple months left so I am trying to get all the small issues fixed before it runs out. I had my car in to my local dealer fixing some issues. I saw that the pinion seal was leaking on the diff. It is not dripping but the front of the diff is wet. My SA confirmed that it is leaking but recommended not to replace it. His reasoning was that the shop foreman said that many times after a pinion seal repair in about a year the car will come back with damaged diff gears?? Any advice on where to take this from here? Have them replace it? Go to a new dealer? Any input would be great.