Interesting report. The arXiv paper is very good read too. https://arxiv.org/pdf/2107.12370.pdf
, 17 pages. I note this in the arxiv paper. "Additionally, the comet’s large ain ≈ 1900 au implies that perihelion activity from previous apparitions will not substantially affect the meteoroid flux at Venus:"
I note *from previous apparitions*. The article states the period is about 80,000 years. "In December, Venus and a long-period comet called Comet C/2021 A1 (Leonard) will nearly cross paths, with the planet crossing the comet's debris trail just three days after the icy body dashes by Venus on its first visit to the inner solar system in some 80,000 years."
I used Jean Meeus solutions and found this period and perihelion distance could be near 3.8 au too (depending upon eccentricity), so inside Venus orbit around the Sun. In one billion years, the comet could complete => 12,000 perihelion *apparitions*. It is apparent that long period comets do not last billions of years in the solar system, so too short period comets.