I think 2 minutes is pretty generous. If it doesn't stop AFKers, it still inconveniences people who don't participate, which is more than enough. Makes it a lot harder to alt-tab and start messaging people on Discord or something when you have specifically queued up for a short 15~ minute activity involving other people. If it's an emergency phone call or something and they have to resolve it, they can go do that and come back and the penalty will be resolved.