What does your work out consist of? I run over 3 1/2 miles every other day.
Mine varies with needs. My primary needs are for competitions, which are the most physically demanding part of my involvement in the fire service. For most of the year, I do a mixture of weights and cardio, though I'm incorporating the cardio component into everyday activities, like cycling when I can. Some running will be needed as well. The gym/cardio routine takes up approximately 6 months, then 3-4 months with some weights combined with competition (pre-season) training, and during the competition season, the competition training itself is all I need. It took 18 months to get myself fit enough (from a reasonable base) to be able to handle the load without injury.
While my training isn't tailored for the fireground, it does help to some extent there as well.