I think 14 is plenty old but not for days on end. My daughter was 13 when I left my kids with her. Never for more than a few hours. And usually, they were all asleep. I worked for the health department and was on call overnight sometimes so I'd leave a note when I left and usually when I got back they were all still asleep. I doubt I would do that now. Although I did let her skip school a few times to stay home and take care of the baby so I could work an extra day! They were 16 years apart.