Just as much info out there says that if a shielded or sealed bearing is suspect or needs grease you can and others say no way. I've cleaned and regreased shielded bearings. I've deduced that it comes down to the application and the industry it is used and that makes total sense. Is a bottom bracket or bike front wheel bearing the same criticality as one in a motor turning 3600 rpm 24x7 in a chemical plant or in the transmission in your car? People with cup and cone clean and regrease all the time for years. In principal, not much different here. It is the application!!!!

If me.. if the act of tearing down and putting back together the BB and cleaning and greasing any threads and all tightened back up doesn't resolve the creak or squeek, then consider the bearing regrease or replace. 6903-2rs are like $10-20 for a pair. I just looked up that BB, MSRP $130-180? Looks like a top notch BB.