Well, I've replaced a cheap cartridge (Chin Heur) after a few K miles with a UN55 that probably has 5K miles on it and running fine. I probably have 10K on an 105 BB5600 HTII bottom bracket that is running fine.
Either one should give years/miles of trouble free service unless you're riding in very extreme conditions.
I would forget the UN 26 and step up to a UN 55 for a few more $$