Off season training?
To the dedicated rider, there is no 'off-season'. Of course, my weekly miles have sure taken a drop lately...
Cross train. Spinner, treadmill, stairstepper, etc... Don't forget the upper body and flexibility work, also.
Here is a link to a firefighter fitness website. It breaks the year down into 3 'seasons', with specific workouts designed for each.
http://www.nifc.gov/FireFit/