Not the most exciting component on your list, I’d guess, but certainly one of the most important. The last thing you want is to cycle a couple of thousand kilometres and have your bottom bracket disintegrate, only to find that no bike shop stocks a replacement to match your cranks. (Just ask Mark.) If you’re really unlucky, that’ll also mean new chainrings, and if your drivetrain is sufficiently worn to induce chain suck, a new chain and cassette. It makes sense, therefore, to get hold of a bottom bracket that you can literally fit and forget.
2013 UPDATE: Kona have now seen fit to move the Explosif into the ultra-niche of 27.5‑inch hardtails; thus I can no longer recommend it as a suitable base for building an expedition bike. Frames of yore (2006–2009), if you can find them, will continue to deal well with off-road adventures, as the article below relates.
Whilst the steel Explosif frame is aimed at the cross-country mountain-biking market, it is not uncommon to see long-distance cycle tourers taking advantage of the increased strength and durability of mountain-bike components, which are naturally more heavy-duty than their road-bike equivalents. We chose the Explosif frame (2007 model) for a number of reasons, not least because we planned to travel in remote corners of the world where tarmac had not yet reached. So far, our expectations have been met, and exceeded in many ways.