Summer , fair weather, and foul weather & Cyclocross, and such, make a big difference.

Wheelspray, of grit gets directed at the BB.. and External is , out there.. by definition.
If you can look outside the bike replacement parts for bearings, when the time comes,

A submersible pump bearing in the same size as your bike uses , can be sought.
or to Phil Wood spec bearing , that is essentially part of their seal quality specification.