I think it will come down to how long you can stand feeling like death. I just saw a video of a guy who ran 250/500/750 a month each and lost 105lbs. I've tried 750 and would never be able to handle a month. I get way too lethargic and my productivity just suffers way too much.
At 500 a day I tend to tap out on day 6....but I usually eat zero cabs while doing a ton of cardio while using dnp to get the maximum benefit.
It's all about how long you can deal with being lethargic and run down....I always wished I didn't have such a physical job (construction) because I just cant run 500 too long before my work starts to suffer and I become unproductive on the job site. Now if I had a work at home job or something like that I think I could run 500 for 2 weeks.