Operational since October 2011, the First G-APD Cherenkov Telescope
(FACT) has been monitoring TeV-blazars. An unbiased observing strategy,
robotic operation and the usage of solid state photo sensors (SiPM, aka
G-APDs) increase the instrument's duty cycle and minimize observational
gaps, making FACT an ideal instrument for long-term monitoring. In more
than eight years, an unprecedented data sample of more than 14700 hours
of physics data has been collected.
Results of an automatic quick-look analysis are published with low
latency on an open-access website. Based on this, close to 150 alerts
including 12 astronomer's telegrams have been issued in six years,
triggering a variety of multi-wavelength studies including
target-of-opportunity observations with X-ray satellites.
Results for various triggered multi-wavelength studies, e.g. Mrk 501 in
2014, 1ES 2344+51.4 in 2016 and Mrk 421 in 2019, are presented together
with long-term studies, like e.g. a multi-wavelength study of 5.5 years
of observations of Mrk 421 and studies on the variability
characteristics of blazars including periodicity studies.