On my last 8-week tour I had a few mechanicals:
1 puncture
3 broken spokes due to chain damaging spokes
Grease washed out of wheel bearings during sea-crossing
General accumulation of dirt on drivetrain.

You should be able to fix a chain, clean and adjust wheel bearings, adjust derailleurs, change a driveside rear spoke, tighten a crank.
The only tool I left out of my kit was a headset wrench and fortunately my headset was the only part of the bike that behaved itself for the whole journey.