How much screen time is actually OK for an 8 year old?

My son has been asking for more gaming time and I honestly don't know what the right answer is. He's doing fine in school, has friends, plays outside sometimes. But on weekends he wants to be on the Switch or watching YouTube constantly. My wife says he's fine, I'm worried he's getting too much. What do you guys do? Are there apps that actually work for limiting screen time or is it just willpower on our part?