Phil Laak played poker for 115 hours straight, which is coming up on 5 days straight.
I don't think you'll get great odds on 3-4 days. If you up it to 5 days or so you might get decent odds.
I think the most I've done was 44-46 but I've never had incentive to go longer. I felt pretty fine when I stayed up that long, but 2 days is nothing