This will depend on the instrument. The tutorial for b600 is here.
First step is to estimate the concentration of the sample based on the residual signal of the solvent. Knowing how long it takes on that instrument to achieve a signal to noise ratio (SNR) in a particular experiment on a sample of known concentration, one can calculate the duration of the experiment on their sample. A minimal SNR is 4. Halving the concentration or doubling the SNR takes 4 times longer.