It's important to build community at the start of the year, so groups certainly have their place, but after week 8 or so, it's time to take it up a notch.
We'll stay in rows for the rest of the year, providing it works for the kids and it seems like it does.
We all rely on partners, be they spouses, team-mates or colleagues. We need these people in our lives to be successful. I want students in my class to not be dependent on me for all the answers. I want them to develop their communications skills and reciprocate support. It makes for a wonderful learning community and builds essential life-long skills for success.
After all, who hasn't ran an email by a colleague before sending to the boss? I want students to start to develop these kinds of habits now. It's a bit old school but like my 1976 blender, it works really well. (Updated in 2014 to add that my '76 blender still works. Still work!)