Would like to say thanks for all the comments.
re availability and durability, I would not be away for a year or something, probably a month or two tops, so within reason I wouldn't have durability concerns, and if I were to go ext bb, it would easy to put in new bearings before the trip, or to simply regrease. I would also want to get significant riding time in on the bike before a trip, and also to get experience doing work on the bb, plus I imagine taking along a spare set of bearings is not an issue, and would be rather light if real concerns about availability were there--this touches on another reason for sticking with mid level shimano stuff, in general, its found in most places, or at least the chances of finding a place with it nearby is a lot better than fancier stuff. Comes back to the "bang for buck" aspect, as availability and commonality is a factor here too.