  Popular Fast Radio Burst models involve rotating magnetized neutron stars,
yet no rotational periodicities have been found. Small datasets exclude exact
periodicity in FRB 121102. Recent observations of over 1500 bursts from each of
FRB 121102 and FRB 20201124A also have not found periodicity. Periodograms of
events with cosine-distributed random offsets as large as $\pm 0.6 P$ from a
strict period $P$ would still reveal the underlying periodicity. The
sensitivity of periodograms of long data series, such as bursts observed on
multiple days, to slow frequency drifts is mitigated by considering individual
observing sessions, and results are shown for FRB 121102. Models of repeating
FRB without intrinsic periodicity are considered, as are models of apparently
non-repeating FRB.
