The primary reason I try to keep my workouts under a half hour is so that I will do them. My mental game has been low for the past 6 months for health reasons (sore elbow, sore hip, hernia, flu, decreased strength) and I am not usually up for a 45-minute to one-hour routine. My cardio work is really not that much. Five minutes on both the rower and speed bag is very minimal in that regard.Do you feel that you're starting to see if the shorter workouts are working for you?
Myself I feel that a more cardio based routine, shorter in duration that my previous workouts, makes for a more energetic day, and following day. I still routinely fall back into a more weight based routine, but do like the more cardio based.