Along the same lines - time to complete a task - I have a similar question. I am looking at a dense point cloud reconstruction (1736 build) that I selected at medium resolution (1447 12 MP images). Right now PS says 27 hours elapsed (about right) and 91 hours remaining. I was surprised at how long it looks like this will take, since I picked medium resolution for both the alignment and the dense pointcloud. I am guessing I will end up with a huge number of points...
The images have a great deal of overlap - the point cloud was derived by attaching a camera with intervalometer to crane and lowering it into a canyon below a dam. Camera is looking downward and slightly obliquely. The crane moves slowly relative to the image frequency (1 image/3 seconds).
System is a dual CPU workstation with two quad core Xeon X5647 (2.93 GHz) CPUs, 192 GB 1333 MHz RAM and a single ATI HD7970 GPU.