Kiwi had the run of our first apartment at about 16 weeks, the reason being he was escaping from every pen/area we put him in! So we figured why not! He had a few accidents but was actually pretty good, we closed the bathroom and bedrooms doors, so he only had the living room and kitchen. When we moved into our current home we still closed the bathroom and 2 bedrooms doors, but he had the rest of the house and was fine by then.(he was just shy of a year when we moved)
Little Lola is now around 14 weeks and has not yet escaped her pen so she still only has her little area. The current plan is to wait until she is 16 weeks and then give her the whole kitchen since she is doing awesome with her potty training and see how she does. We will then probably slowly increase her area as we feel comfortable with her training!
