I have four units. I upgraded to an orbi last year.  These work fine and I actually like the Amazon software better than the more expensive Orbi software. The Erros do sometimes lose their connections but they're pretty decent. If someone wants all four, they can have all four but I can also split them up. Even a single one works fine as a standalone Wi-Fi router, But that's kind of a waste since they're all meshwork and work together.  So spreading out to three or even four of them in a larger building is where you get the most gain.  Depending on what your walls are made of 3 to 4 units can easily cover 2000 to 3000 square feet.