The amount and type of calibration data you require depends critically on what you are doing. We'll begin by briefly reviewing the type of calibration data that may be required, along with our recommendations. You may wish to take three frames of the same length of time as your longest exposure to evaluate how much dark current is contributing if you are attempting to do long-slit spectrophotometry without local sky subtraction. In practice, the dark current on all three of these chips is fairly minimal. Be sure to make these exposures with the dome dark.
All spectrographs have some minimal amount of flexure.
If you are satisfied with shifts of a pixel or two, then a single comparison exposure in the afternoon is good enough. The thorium-argon source should be used for higher dispersion applications. At the 2.1-m the only comparison source is a HeNeA source. Projector flats can be run in a few minutes without moving the telescope, and so are fast and convenient. However, the large scale stucture does not match the night sky very well.