I have a 10 and 9 year old and I haven't left either in the house on their own yet, but I feel the time is approaching. I couldn't leave them both though as too much capacity for mischief. What I worry about is more something happening to me when I am out, e.g. flat tyre or something and not being back in the 20 minutes. I have left them for a few minutes playing in the street with a neighbour being aware that I am out, if for example I am nipping round the corner to get the other one home from a friends.