when did you first allow your child to stay at a sleepover?

my daughter stayed at a sleepover when she was 8. this is a family we have known for years and are comfortable with. also, they have a daughter of the same age, so we were comfortable that our girl would be safe and alright.

i let my daughter stay over at her friend's place when she was 9. also, as this friend is in the same building as ours, it was not really a problem.