I do my best to stay in shape year around, but recently got a new toy that gives me some feedback about my hiking workouts. It is a Fitbit, a little gizmo that clips to my pants pocket, and is like a pedometer on steroids. It measures steps, miles, 'floors' (each 10 feet of ascent is a floor), and links with my computer to log data into a web page. You can also use it to log food eaten, sleep, bp and heartrate, etc. Unfortuneately, it doesn't work with bicycling, but it seems very accurate with hiking/jogging. Just another option if you want to log your workouts, and somewhat of a motivator, too.
I, too, am spending time in the warmth of the Sonoran desert in the winter, and getting in 6 to 7 mile hikes just about every day. Sure beats shoveling snow.