"You've got to value your time, you cannot just assume that you're going to get to retirement and live this life, you've got to go and do what you want now," Butter told CNN.
Butter ran Sunday in a marathon in Greece, the final country on his world tour.
The runner said he ran in organized marathons whenever possible, but often found himself having to chart and document his own 26.2-mile courses.
He said his project had numerous ups and downs.
"I was bitten by a dog, I was mugged, I was robbed at knifepoint, I was put in a cell," he said. "I ran with a thousand people in El Salvador, I ran around erupting volcanoes."
Butter, whose lifetime marathon count is now 592, said he doesn't plan to slow down now that his world tour is complete.
"I'll have a couple of days off but I actually am kind of itching to get running again," he said. "It's my thing."
