Hi S.,
My kids are young but the way I've seen my sister do it works great. She is very strict.
They get 3 days a week thet can pick which days and they get a certain amount of time. I believe during the week 2 hours each time they play and weekends a little more, say 3 hours.
They can no play on the off days and they can not go over, once you compromise, they won't take your rule seriously.
Her kids are both doing great in school, active in other activities like soccer, tawkwan do, etc.
In the long run, rules aren't for your benefit but for theirs. If they don't learn moderation as children, they will struggle to moderate "pleasurable" from the mundane we all have to do....
I see it with many kids, they no longer care for social interaction, they don't excell in school and have basically no self control.
They do poorly in life in general.
M