IMO- You should ride the Brooks as much as you can before the trip. I use a plastic shower caps as seat covers, but translucent plastic act like a greenhouse. I don't usually leave them on for extended periods or when it is really sunny. The heat can really build up inside. I'm not sure, but this might help during the breakin period. Anyway, it is something to think about.
I usually repack my wheels before any major tour using Phil Woods waterproof grease. Like njkayaker said, "At least cup-and-cone hubs are easy to service (and it looks like you'll get lots of practice)"