  BGP exchanges reachability information in the form of prefixes, which are
usually originated by a single Autonomous System (AS). If multiple ASes
originate the same prefix, this is referred to as a Multiple Origin ASes (MOAS)
prefix. One reason for MOAS prefixes are BGP prefix hijacks, which are mostly
short-lived and have been studied extensively in the past years. In contrast to
short-lived MOAS, long-lived MOAS have remained largely understudied. In this
paper, we focus on long-lived MOAS prefixes and perform an in-depth study over
six years. We identify around 24k long-lived MOAS prefixes in IPv4 and 1.4k in
IPv6 being announced in January 2023. By analyzing the RPKI status we find that
more than 40% of MOAS prefixes have all origins registered correctly, with only
a minority of MOAS having invalid origins. Moreover, we find that the most
prominent CIDR size of MOAS prefixes is /24 for IPv4 and /48 for IPv6,
suggesting their use for fine-grained traffic steering. We attribute a
considerable number of MOAS prefixes to mergers and acquisitions of companies.
Additionally, more than 90% of MOAS prefixes are originated by two origin ASes,
with the majority of detected origin AS relations being customer-provider.
Finally, we identify that the majority of MOAS users are IT companies, and just
0.9% of IPv4 MOAS and 6.3% of IPv6 MOAS prefixes are used for anycast.
