I have one cat and I scoop at least once a day, sometimes twice. But I think if for some reason the litter couldn't get scooped for a full day, it wouldn't be all that terrible. I have no reason not to scoop everyday, but if I was sick and had no help, I could see scooping every other day or something.
Anymore than that and things would get pretty disgusting. Plus, that's just with one cat. With 2 cats I think at least a daily scooping is a must.