I've been building my own wheels for several years now because I was trashing everything I rode. I'm 225lbs and I've seen no need
so far to go to 36 spokes. On my XC disc 29er wheels I have been running DT Supercomp triple butted spokes and alloy nipples, 32 spoke, 3 cross, with no issues, even on a single speed. I also use this combination on my no-brake/fixed gear bike that is using Velocity Blunt MTB rims and cyclocross tires on track hubs. The fixed gear sees a lot of rough dirt road riding and the wheels are holding up fine. I also build a lot of BMX wheels 32/3 and have not had a single wheel come back for truing. If you are going to be running front and rear racks and loading it to the hit for an "Around the World" trip you may want to move up to 36/3 cross or even 36/4 cross, but with modern metallurgy being what it is, 32/3 wheels are incredibly strong if built right with quality components.
I'm starting my first bikepacking/touring bike project myself and will be using Hope Pro2 hubs with the steel freehub body upgrade, Velocity P-35 rims, DT Competition double butted spokes and brass nipples, 32 spoke, 3cross. These are not cheap components but Hope hubs, Velocity rims with DT spokes have proven to be bulletproof for me. I just built this exact same wheelset for Scott Brady of Overland Journal/Expedition Portal for his adventure bike project.
http://www.expeditionportal.com/forum/showthread.php?t=44361