Potential Problem 320I E90

I recently took my 2006 320I E90 for a computer check up for a upcoming long distance trip. The car has 116,000 on the clock The Workshop was not a BMW dealership, as I prefer 2nd opinions, but specializes in BMW and Mercedes. Before I left they advised me that they had to replace a number of E90 alternators at early mileages without,for example, the option of replacing brushes.
Have any E90's out there experienced this problem?