Once a day, usually. I eat a lot of vegetables now, when I first started 'paleo' and didn't, it was more often every other day. Pre-paleo at the height of my IBS, as much as 8 times daily. D:
Fat, protein and simple starches are almost completely absorbed by the body. Unless you are eating ample amounts of veg (and or fruit, and nuts) - a paleo diet can be what is medically defined as a 'low-residue diet'. IE one specifically designed to produce almost no solid waste. Considering this, it's definitely not surprising to me that so many people eating this way don't poop a lot.
There is no evidence I've ever seen that it's objectively healthier to poop more. What matters is stool quality and consistency, not frequency. Human poop should have some structure, yet be soft enough to be passed comfortably and quickly. It should not be dry or compacted (and painful or strenuous to pass), neither should it be liquid-y or contain undigested fat or food. As long as your poop is within those parameters indicating good gut health and proper digestion, it doesn't matter at all whether you go twice a week or twice a day.