I can't imagine anyone being happy with 1. That's 5 days of complete unresponsiveness. They don't know that they will blacked out for 5 days and neither do you. And even worse, what happens if at the end of 5 days you realize you took a wrong path on day 2? Now you still have to talk to them after ignoring them for a business week.
Personally, if I got blacked out like this there better have been a death in the family or I'll never work with this person/agency again and will heavily recommend against having anything to do with them.
Well, it's not a complete blackout; you can provide the 5-day estimate beforehand, you can send progress reports or two along the way.
The point is, they still are much more comfortable with the demonstration that you are willing to spend as much time as it takes to calm them down in person, progress on the product be damned.
Personally, if I got blacked out like this there better have been a death in the family or I'll never work with this person/agency again and will heavily recommend against having anything to do with them.