@User: Yes, ngspice is very slow, and I've noticed one bothersome thing, which is that if there is an error in one of the files that is not the corner being chosen, then ngspice will flag it---which means that ngspice is reading all of the included files in that library, not just the ones belonging to the corner being simulated. I would think that's a low-hanging fruit for ngspice performance optimization. . .

Yes, I commented out the other corners from the lib file as well. I thought the same, probably some really nice wins that can be made by looking at the CPU time spent :-)