Some more detail here:
Here is a larger molecule, cembrane (pubchem link) which has 20 carbons. The run is longer, too, with 2,000 steps. It finds a spectrum with 100% match within 300 steps, in this case.
An even larger example is lanosterol (pubchem link) which has 30 carbons. This actually seems to be too large for C-NMR prediction using NMRShiftDB. It doesn't get the answer within 2,000 steps, and does not look like it is on course to do so: