The fact a team as well prepared and supported as Keith's indicates how difficult the Cannonball is. This year 20% of the entrants managed to make fewer than one-third the miles, and only 37% managed to cover all the miles.
It's remarkable what things can be repaired when they must be repaired. Fully 75% of the entrants were on Harleys or Indians so if one of them needed a spare part to replace something un-repairable that they didn't have there was a reasonable chance they could find it from one of the others. However, Team Norton's Nortons were the only English bikes in this year's Cannonball, so if they couldn't fix whatever broke, or have a spare (or spare spare, if it broke twice) to replace it, they were out of luck.
Covering ~3400 miles on the Cannonball with a bike that's 90+ years old is nothing like doing the same thing with a few friends and no fixed schedule, let alone on a series of day trips based at your own home. On the Cannonball you must leave early each morning and must arrive at the destination by a certain time late in the afternoon. Then eat, spend whatever time is needed to fix everything that needs to be fixed (in a motel parking lot, at night, possibly in the wind and rain, and with whatever tools and spare parts you have), sleep, pack, and do it all over again thirteen more times.