35 for the 5 of us (2 adults plus three school-age kids).
It's a nice idea, but in terms of setup and design, this is one of the worst online surveys I've seen and that's saying a lot. In scope it's quite similar to the 'ecological footprint' surveys I've helped conduct for a local environmental group, but those can be completed in about a quarter of the time this one took.
Also, glad they had those 'fine tune your results' sidebars, since some of the defaults were ridiculous (apparently my kids each have a cell phone, game console, action figure, cycling shorts, and rain boots--none of which any of them have--yet I'm making them get by with just 2 pairs of underwear between them??).