I'm now in third year, and I started looking around January/February and found my house in the March. It depends whether you plan to stay on campus (if your uni even offers that, I don't know) or go off campus, and if so where.
At my uni, people definitely still go out, however I'm at a rural uni so there aren't any clubs, just the SU and some pubs in town. People did seem to calm down a bit, as second year grades counted, but they still attended weekend events just maybe not every one due to deadlines.
Does that help? It's tricky as these are things that differ due to experience, as I am sure you can appreciate.