I am a molecular biologist, and it kinda works this way. B cells are called memory cells because they hold onto that "memory" of the invader for a really long time. You probably haven't had an MMR or a Tetanus vaccine in 10+ years because the body is really good at remembering. But we have to get flu boosters every year because the flu mutates so rapidly that traditional b cells won't recognize the flu after a year of mutating. (RNA viruses can't correct their mutations so they change much faster than bacteria or DNA viruses). RNAi was still pretty new when I was in school and I haven't kept up with the research so I can't speak to it's effectiveness at long term immunity.

It is good that you recognize that you don't know enough to dispute it. Now just recognize that people who do know enough aren't disputing it.

I assumed it had to do with heartbeats. Mice hearts beat much faster than human hearts, and I think of the heartbeat like a computer’s clock or an engine’s RPM. If you increase that, the rate of everything else increases.