Small aside: The person at the start (Gary Flook), served for 37 years in the Airforce and found out he had cancer at age 45. Was he 8 years old when he started serving? Or started at 18, got cancer then kept serving for another 10 years?
37 years is anything except normal, however looking him up (he is trivially found on Facebook) he retired as an E-9. That rank is exempted from Time In Service (TIS) limits as they serve all Commanders as advisory and enlisted liaisons. He also states he is retired Civil Service, so they may be conflating that time.
In other words, he probably served for 37 years but a huge chunk of that was likely as a Flag (Admiral/General) advisor and liaison, not as a firefighter, and some as a DOD Civilian.
As for the cancer, some cancers can be cleared by a Medical Evaluation Board (MEB) and allow further service. I served with an individual who got brain cancer at ~30 and went on to finish his career and retire at 40.
He was 45 in the year 2000 when he discovered he had testicular cancer. Presumably he had that treated and continued his military career, eventually retiring after 37 years of service. If he’s 68 now, a 37 year military career is pretty normal.
Or did he serve 27 years and it's a mistake.