Just like you, I listen to what experienced mechanics have to say. The problem is they don't all agree and frequently they don't agree even with themselves.
One very experienced mechanic told me to change the filter every other oil change. Some say to change the oil every 3000 miles, others say 5000 miles. The whole synthetic thing has the mechanical community in an uproar. Some say once you go to synthetic, you can never go back to regular oil. Someone told me synthetic in my motorcycle would make the clutch slip.
I really don't think that is the group to look to for consensus about taking care of a car that breaks as many rules as Mini does.
Call your service department and ask them.