Generalised recommendation for a single target. Top panel: a flow chart that observers may consult while planning their observations. First, observers should consider their instrument and system parameters. For lower spectral resolutions (R) and longer transit durations (t_d), longer exposures may be prioritised; for the inverse case, shorter exposures are more suitable. For other cases, the choice is determined by what signal strength is possible. Bottom panel: the logic of the top schematic is illustrated here. Smearing is more of a concern for low R and long t_d (case A) and less of a concern for the inverse (case B). For all other cases (C, D, E), a larger concern for signal (i.e. lower signal strength) encourages longer exposures and a lesser concern encourages shorter exposures.