How long should our TV group chat wait before discussing the finale?

At 6:14 in the morning, our group chat had a message saying, 'Don't worry, I won't say who survives.' That was enough to tell me the finale wasn't just going to be about the missing money.

Six of us have been watching the same mystery series. Four watched the finale when it appeared overnight. I was getting ready for an early shift, and another friend couldn't watch until Sunday. We had agreed to avoid spoilers, but never said for how long or whether reactions counted.

I asked everyone to wait until Sunday evening. One friend said, 'That's the only thing we've all been excited about this week. Can't you mute us?' It's also our chat for dinner plans, so muting it means missing those. I suggested a separate finale chat; the friend who usually organises everything said she didn't want another group to manage.

I don't expect the whole internet to wait. I'm trying to keep the conversation with these five people. What would be a fair agreement that lets them enjoy the finale without making the two late viewers disappear for three days?