This study investigates the long-term stability of the human gut microbiota using a low-error 16S rRNA amplicon sequencing method (LEA-Seq) and whole genome sequencing of cultured isolates from 37 USA adults over up to five years. The results show that the microbiota stability follows a power law function, suggesting that most strains in an individual's gut are residents for decades. Shared strains were found in family members but not in unrelated individuals. Weight changes were more predictive of changes in strain composition than sampling intervals. The combination of stability and responsiveness to physiological changes highlights the potential of the gut microbiota as a diagnostic tool and therapeutic target. The study also demonstrates the utility of LEA-Seq for high-precision amplicon sequencing and the value of culturing and sequencing anaerobic bacteria to understand the dynamics and stability of the microbiota over an individual's lifespan.This study investigates the long-term stability of the human gut microbiota using a low-error 16S rRNA amplicon sequencing method (LEA-Seq) and whole genome sequencing of cultured isolates from 37 USA adults over up to five years. The results show that the microbiota stability follows a power law function, suggesting that most strains in an individual's gut are residents for decades. Shared strains were found in family members but not in unrelated individuals. Weight changes were more predictive of changes in strain composition than sampling intervals. The combination of stability and responsiveness to physiological changes highlights the potential of the gut microbiota as a diagnostic tool and therapeutic target. The study also demonstrates the utility of LEA-Seq for high-precision amplicon sequencing and the value of culturing and sequencing anaerobic bacteria to understand the dynamics and stability of the microbiota over an individual's lifespan.