The farthest I have gone so far to look at and try a horse was about 4 hours, but I would go farther.
As an eventer, I need something that is very sound and will stay sound. Plus a large list of other things that make a horse suitable for the strenuous work that eventing is. Because I plan on competing at the upper levels within the next 10 years, I've given myself even higher standards than before, simply because I want my next investment to really be worth the money I pay and because I know how high the demands are on an eventing horse doing Preliminary (two levels under advanced/olympic level, not sure what it's called in other countries) and above. I want to be sure the horse I end up buying has the mentality, athleticism, and soundness to succeed, because as stuck up as it sounds, I compete to place top 5 or win, and anything less than that (even if it is a very good ride) is not good enough because I want to be constantly improving.
"Always be yourself. Unless you can be a unicorn. Then, always be a unicorn."