  Aims. We attempt to determine if a dependency on spectral subtype or vsini
exists for stars undergoing phase-changes between B and Be states, as well as
for those stars exhibiting variability in H{\alpha} emission. Methods. We
analyse the changes in H{\alpha} line strength for a sample of 55 Be stars of
varying spectral types and luminosity classes using five epochs of observations
taken over a ten year period between 1998 and 2010. Results. We find i) that
the typical timescale between which full phase transitions occur is most likely
of the order of centuries, although no dependency on spectral subtype or vsini
could be determined due to the low frequency of phase-changing events observed
in our sample, ii) that stars with earlier spectral types and larger values of
vsini show a greater degree of variability in H{\alpha} emission over the
timescales probed in this study, and iii) a trend of increasing variability
between the shortest and longest baselines for stars of later spectral types
and with smaller values of vsini.
