Originally I was going to work super hard to try to save up so much money by 40, but this sounds much more fun. Because 40 might slip to 45, 45 might slip to 50 and then I waste it what's left of my youth chasing money instead of seeing the world.
In much of the world you can live very well off of $1,500 a month, if you have a job which lets you save $30,000 a year, you can afford to only work every other year.