Knowing his to fix your bike is really important as well. Simple stuff like replacing links in a chain can really make a difference and you will have to put a lot of maintenance along the way. My first tour was when I was 19 (San Francisco. - DC). And I knew little about repairing my bike. I had some uncertain times with my bike and was my biggest regret.A good quality bike in well maintained condition should not require a lot of maintenance even over a 4000 mile tour. Chain lubing and tire pressure should be the only routine items with wearing out or damaging a tire as a possibility. If you start with the components in good shape cables, shifters, brake pads, chains, wheels, etc. should last the duration of the trip with no problems. The operative term is "good quality" and X-Mart level bikes don't qualify.
However, that's not to say bad things can't happen even to good bikes so knowing how to do your own repairs and having a few essential tools (Allen wrenches, chain tool, tire levers, etc.) and spare parts (shift and brake cable, brake pads, tubes, chain master link or joining pins) should be considered essential as is the ability to use them.