We've sold 2 homes and this has never happened.
After the contract signing, the new owners to be did show up with the inspector which is perfectly acceptable and then they did not come back until the day we closed.
It would annoy me if someone wanted continued visits because in my mind... I would think they were looking for anything they might have missed so they could pin in on you, second guessing themselves, etc. The more opportunity you give them to come look around, the bigger then chance of them having a change of mind.
I think you have gone above and beyond what I would do in this situation. You are trying to pack, clean and have it move in ready for them and they are taking your time away from you.
I'd have the realtor convey that although they are excited, blah blah, that the next time they come in, it will be after closing when it is their new home.