I had to switch to movable lights because building stationary light became too heavy: to get some semi-decent shadows, I had to use lightmaps between 512 and 2048 px, and that’s too much for my 8 gigabytes of RAM.
Of course, the biggest meshes are split in smaller ones. Splitting them further would be really a pain, but maybe that could be a partial solution. I also had lots of problem with blurry shadows. Never been able to solve them, so I’m trying to switch to dynamic lights, since several users in the past suggested they are better for bigger maps.