i would think that reducing weight from the crank would prolong bearing life....less weight...less stress?

 

Less weight less stress sure, but with the chance of it being unbalanced and having the extra vibration would wear bearings even more....But if you had a company like FFWD or GSC sell the crank with a full rotating assembly already balanced perfectly, I wouldn't do it.

 

its not the sheer weight that shortens bearing life, its the amount of the counter weights on the crank that are taken off. Because you balance a crank on the counter weights and with less metal there, the harder it is to balance