About 3 days seems about the max for me if my goal is a huge load. If I'm expecting a possible titty fuck or blowjob I'll hold off for 3 days and that give me the biggest load and distance. If I go more than 3 days it kinda defeats the purpose.
Also, I try and bring myself to orgasm a couple of times during the 3 days and hold off just before. Seems to make the eventual orgasm that much better in volume as well as sensation/feeling.