what is the normal mileage engine mount and differential bushings need replacing

What is your question?

the dealer told me I need engine mount and differential bushings ( cracked) on a 2016 bmw 528i 47K miles.

What makes this problem better or worse?

I didnt notice anything. went in to dealer for covered maintenance

How long has your 2016 BMW 528i had this problem?

I dont hear anything