  Within academia, mature researchers tend to be more senior, but do they also
tend to write higher impact articles? This article assesses long-term
publishing (16+ years) United States (US) researchers, contrasting them with
shorter-term publishing researchers (1, 6 or 10 years). A long-term US
researcher is operationalised as having a first Scopus-indexed journal article
in exactly 2001 and one in 2016-2019, with US main affiliations in their first
and last articles. Researchers publishing in large teams (11+ authors) were
excluded. The average field and year normalised citation impact of long- and
shorter-term US researchers' journal articles decreases over time relative to
the national average, with especially large falls to the last articles
published that may be at least partly due to a decline in self-citations. In
many cases researchers start by publishing above US average citation impact
research and end by publishing below US average citation impact research. Thus,
research managers should not assume that senior researchers will usually write
the highest impact papers.
