To all you 29er's out there!

IME it's primarily because people install them incorrectly. Overtightened and/or on un-faced bb shells which side loads the bearing and dramatically reduces their life. In the five years or so I've been using external bb's I haven't noticed any significant difference in longevity.

Sam

i second that! i am guilty of installing an external BB on a bb without facing and it didn't do much for the wear, but in my experience they are last as long (maybe longer?) and feel stiffer than any square taper i have used.

p.s ISIS bb's blow. fact.