Window Regulator Failed problems of the 2000 BMW 3 Series

The window regulator (I. E. , the mechanical mechanism in the doors which raises and lowers the windows) appears to be faulty. I have replaced the regulators 6 times since 2000. These are repeated failures: the right front window regulator has failed twice (2003 and 2009); the left front regulator has failed twice (2003 and 2011); the left rear has failed once (2008) and the right rear has failed once (2007). BMW only covered the failures under the original warranty (2003). The others have been at my cost.