Run Until You Drop

So during my run on Thursday, when I'm normally thinking to myself "WHY do I do this?" and it's 85 degrees and I'm dying, I came up with a great idea. Someday I'd like to do a run for charity, basically just running as much as I can without stopping (other than bathroom/water breaks) or for 24 hours or something. Donations are per mile. I'm sure there are lots of things to consider and plan for...perhaps I should start making a list. I expect I can do at least 30...