I ran the Great Wall Marathon in 2015 and have plans to run the Big 5 in South Africa to celebrate my retirement.  I have run many marathons and ultras, mostly in Colorado.  My PR is very respectable and have run other very solid times.  Those days are behind me.  My marathons these days will take me to other parts of the country and the world and I don't care about my time.  I recommend combining your passion and travel as these events allow runners to do.