Graham, and it does run out in spades.
In theory 85% exists but it is not all joined up.
In theory it is 2300-400 miles as it changed a bit over the years. So yes at 240 miles a day you can drive but maybe not enjoy it. There is a very good map you can buy which has the best directions.
Each to there own but we wanted to see things like the Grand Canyon etc.
Kerouac's characters meander about not over route 66 totally and generally from NY to LA via Denver. It isn't frankly the easiest read.
