I don't have an in between season thing happening, ever. From November-January my daughter, and to a much lesser extent me, are training for the ABS bouldering comps, so we hit the gym 2-3 times a week. Of course we both continue to climb rock outdoors on decent days, which are more plentiful even throughout the winter if we make the trek to Lincoln Woods or maybe Rumney.
Beginning in January I coach the Junior team at Dover Indoor Climbing Gym to gear the kids up for the USCCA (now USA Climbing) Junior season, which runs through Nationals in July. Meaghan and I will fit the rock in whenever we can in between her competition schedule.
If the weather is bad or I'm taking a rest day for my tendons, then I will drive 5 minutes to Mt. Major and try to beat my round trip time on the 4+/- mile loop. Otherwise stretching or maybe a hangboard workout.