They do go away, but it depends on numerous factors. In humans, if you have polymorphisms in various genes relating to GSH detoxification, the half life could increase. (in theory)

half-lives of long-chain PFAS were longer than those of short-chain compounds, reaching almost 3 years in some cases. Some studies estimated the average half-lives for PFHxS at 2.86 years and L-PFOS (a specific form of perfluorooctane sulfonic acid, C8) at 2.91 years. In comparison, the short-chain PFPeS had an estimated average half-life of 0.63 years, and perfluoroheptane sulfonic acid (PFHpS, C7) concentrations were 1.46 years. The shortest estimated half-lives were for perfluorobutanoic acid (PFBA, C4) at 0.12 years and perfluoroheptanoic acid (PFHpA, C7) at 0.17 years.