I'm about to embark on what I'm fairly certain is my longest single destination journey*. 30 hours. Of course, India/Nepal comes to mind but that was destined (according to nature) to take quicker. Also, that was super fun and adventurous and entertaining and culturally tsunamic so doesn't quite count.
Ahh, am I not the luckiest gal on the planet??
*barring cheeky possibilities such as "life", "happiness" or the like.