I was just giving what seemed like a theoretical max. I would not waste my time doing what I described nor do I have a walmart near me. 100k mile/80k mile cap though is pretty easy to obtain over the course of a year though.
I dont know about pretty easy. Any transaction over 3k requires Wallly World to fill out a SAR report using your DL or ID to document. So you would need atleast 30 trips to Wally World.