This paper presents a new model for examining fission-track data from natural specimens, based on laboratory data describing fission-track annealing in various apatites and empirical corrections for fission-track length anisotropy. The authors use revised and simplified statistical methods to evaluate how well various empirical equations fit laboratory data and reproduce expected behavior over geological time scales. They find that "fanning Arrhenius" models of mean track length are not the best fit for their data, instead suggesting that a model incorporating curvature on an Arrhenius plot better aligns with geological benchmarks. The study also examines the relative annealing behavior of different apatites and finds that any two apatites can be well-reproduced by a simple one- or two-parameter equation. This equation is used to convert the reduced fission-track length of one apatite with a certain time-temperature history into the length of a less-resistant apatite with the same history. The resulting model encompasses the annealing behavior of all studied apatites and matches closely with individual apatite data, suggesting it is an excellent practical solution for characterizing the kinetic variability of fission-track annealing in apatite.This paper presents a new model for examining fission-track data from natural specimens, based on laboratory data describing fission-track annealing in various apatites and empirical corrections for fission-track length anisotropy. The authors use revised and simplified statistical methods to evaluate how well various empirical equations fit laboratory data and reproduce expected behavior over geological time scales. They find that "fanning Arrhenius" models of mean track length are not the best fit for their data, instead suggesting that a model incorporating curvature on an Arrhenius plot better aligns with geological benchmarks. The study also examines the relative annealing behavior of different apatites and finds that any two apatites can be well-reproduced by a simple one- or two-parameter equation. This equation is used to convert the reduced fission-track length of one apatite with a certain time-temperature history into the length of a less-resistant apatite with the same history. The resulting model encompasses the annealing behavior of all studied apatites and matches closely with individual apatite data, suggesting it is an excellent practical solution for characterizing the kinetic variability of fission-track annealing in apatite.