I've never had any opportunity (yet) to do anything really crazy for miles (flying out of CHA limits you in that regard). However...
the Marriot 15k points for five stays paid with a Visa was another matter. I'd had three Nashville trips in the period (oddly, at a different Courtyard each time) plus a seminar at the conference center in Chicago. And so, to finish it off, I spent a night at a Fairfield in literal walking distance of my house!