I know- everyone's different, but I usually just focus on slower, more drill type things in the off-season. I try to swim about 3-4 days a week, but only for about 20-30 min. each time (nice and short, but enough to keep me in swim shape). Each session is only about 1000 yds, but I rotate the type of swimming I do: one time it's a long, slow 1000, next time it's 100 repeats (alternating moderate and easy), another time it's 50's with drills.

I do like the swim workouts in a binder, but always forget to put it in my bag after I've taken it out to dry off (it molded on me once ).