What age for letting a child stay home alone?

I know we have done this one before but I couldn't find the last post.

At what age would you be comfortable with your child staying home alone? I'll break it down a bit further too:

1. For a few minutes while you are within sight of your home?
2. For a few minutes while you run to the store?
3. For a longer period of time, say when you have a doctors appointment.
4. Overnight?

Just curious what others think!

    I will hang out outside sometimes at our neighbors house while the kids are in bed but we can clearly see our house and front door from their porch. And we take turns checking on them. But they literally live 10 feet away.
      I think 1 and 2 are about the same for me, and I'm thinking 12. A longer period of time is more 13-14, and overnight, at least 16.
        I was 8.5 when my mom would run to the store for a few things and leave me home.
        I was 10 when she left me home fir a few hrs after school while she was working.
        By 12 i was home by myself all day and babysitting other kids.

        My 2older boys are not mature enoug. I think i will wait until haiden is at least 9.5 years old for a few mins while i took logan and vince with me to a store.
        For longer i would wait til at least 11years old.
        About Melissa
        Birth: December 31
        On Moms.com since: Mar 3, 2014
        I am a single mom of two fantastic kiddos that I love to pieces. Currently in school working towards my teaching degree. You can find me most days on www.mommathoughts.com when I am not here chit chatting! :)