Maybe I am reading this wrong but I have 24mm Shimano 6800 cranks with external BB. I have 23,000 miles on them and they spin like a top. I have never touched them. On all my previous bikes I have used external bearing BB with Shimano Cranks. These include 6600, 6700, and 7800 durace, and never have had to replace or service a BB on any of those bikes. They are HT cranks right? In fact I plan never to buy a bike with press fit BB due to the inherent problem that seems to be, although some have done better that others, never will they exceed the external threaded BB for ease of use.