Hours and hours.
We are blessed to have a park literally on our doorstep (my front gate opens into it!) so in the summer they're out there with all the other children on the estate for hours.
Today they got home at 3.30, and I managed to drag them in for half an hour for tea and they were then back out there until 9. No doubt tomorrow they'll be out there first thing!
In the holidays they can be out there literally all day and all of the parents take it turns in taking out a plate of sandwiches and crisps at lunchtime, bottles of squash and ice lollies. There's always bike and scooters and various toys out there and they all just share, can be about 20 kids out there sometimes aged from 3 up to 16 just playing together. They play all old fashioned games like chase and duck duck goose and it's lovely to see the teens (boys and girls!) facilitaring the games for the younger ones
Sometimes we even brave the tuff spot with some paint and paper and put it in the front garden and have multiple kids in and out just painting and drawing.
We all tend to call our kids in the same time on an evening and they all, without being printed, help collect all the toys, make sure they've left no rubbish etc.
In the winter not quite as much obviously, as it's just grass other than round the play equipment so it can be very muddy, but if it's dry, they're out there!
It's absolutely wonderful!