How many rough cuts of my friend's short film should I give feedback on?

The fourth video arrived with, 'Almost there. Can you watch tonight and send time-stamped notes?' I'd offered to watch one rough cut, three Sundays ago.

My friend has made a twelve-minute short film. I watched the first version twice and said I lost track of who knew about the missing key. He changed the opening, then sent two more versions. I've tried to be useful, but each viewing has become a longer message about smaller choices.

He now asks which individual shots to remove. I'm his friend, not someone with editing expertise, and I don't want him to think my taste is a professional answer. He says a fresh pair of eyes is all he needs. Mine don't feel fresh anymore.

I want to celebrate the finished film. I don't want to spend every evening before it is finished deciding whether a doorway shot should last two seconds or three. How do I stop helping without leaving him with the impression that this cut must be ready because I've gone quiet?