  We present results of our analysis of up to 15 years of photometric data from
eight AM CVn systems with orbital periods between 22.5 and 26.8 min. Our data
has been collected from the GOTO, ZTF, Pan-STARRS, ASAS-SN and Catalina all-sky
surveys and amateur observations collated by the AAVSO. We find evidence that
these interacting ultra-compact binaries show a similar diversity of long term
optical properties as the hydrogen accreting dwarf novae. We found that AM CVn
systems in the previously identified accretion disc instability region are not
a homogenous group. Various members of the analysed sample exhibit behaviour
reminiscent of Z Cam systems with long super outbursts and standstills, SU UMa
systems with regular, shorter super outbursts, and nova-like systems which
appear only in a high state. The addition of TESS full frame images of one of
these systems, KL Dra, reveals the first evidence for normal outbursts
appearing as a precursor to super outbursts in an AM CVn system. Our results
will inform theoretical modelling of the outbursts of hydrogen deficient
systems.
