  We report the results of 10 years of monitoring of six regularly varying 6.7
GHz methanol masers using the Hartebeesthoek 26m telescope. Observations were
done at intervals of 1--2 weeks, with faster sampling during flaring episodes.
Four of the sources were also monitored at 12.2 GHz and show correlated
variations. We find the Lomb-Scargle periodogram to be the most sensitive
method to search for periodicity but possibly prone to false detections.
Periods range from 132.8 days (with 26 cycles observed) to 509 days (with 7
cycles observed). Five of the sources show arguably periodic variations, while
G331.13-0.24 shows strong periodicity in one peak, with large and variable
delays in other peaks.
