My 7yo is obsessed with Roblox - when do I pump the brakes?

So my son just discovered Roblox and suddenly he wants to play literally every waking moment. He's spending like 2-3 hours a day on it, which I know is way too much for a 2nd grader. The thing is, he's actually doing math in some of these games (currency, trading, etc) so it doesn't feel completely brain-dead like YouTube shorts. But I'm worried about addiction and also the social stuff - he's chatting with random kids and I have no idea what they're saying to him.

Where do you guys draw the line? Should I let him have weekends free? Limit it to 45 mins on school nights? I feel like I'm making this up as I go.