Lifetimes of starspots can be determined from long-term observations which are, for instance, provided
by continuous photometric data. Hall and Henry (1994) analysed several dozen spotted stars and concluded
that lifetimes of relatively small spots are proportional to their sizes, which is consistent with sunspot
properties. Lifetimes of relatively large spots are possibly limited by a shear of surface differential rotation.
On the other hand, large spots causing prominent light curve minima apparently can survive for many
years, despite differential rotation, and form centres of activity, or active longitudes (see Section 5.4).
This may even be true for pre-main-sequence stars. For instance, based on a comparison of
the Doppler image with photometric spot models, Hatzes (1995) suggested that the spot on
V410 Tau has survived on the stellar surface for about 20 yr. Doppler images suggest, however,
that these regions often consist of several smaller spots. Lifetimes of those spots are yet to be