In addition, there are a bunch of premixes that are shorter lengths. Do you have the "Cathe Compendium" link? The Cathe compendium has a wealth of information! I refer to it a lot. One of the things it lists is all of the premixes available on most of her dvds and they list the length of the premix.
I just looked at it for you and found that Kick, Punch, and Crunch has a 37 min cardio conditioning, a 42 min intermiediate intensity drills + combo 1 & 2 (kickbox combos and drills)
Drill max: timesaver cardio blast - 39 min (probably has some step in it though, but not complicated step)
Bootcamp (from Intensity Series, Muscle Endurance & boot camp workouts)
cardio only - 20 min
cardio & lower body 34 min
Plus the new Shock cardio that will be coming out shortly is supposed to have 2 HIIT workouts that are ~ 20 min long (I think).
And like the previous post mentioned 4 DS has 4 30 min cardio workouts - all of which are great. The step workouts are a bit on the complicated side - but really fun if you like that sort of thing.
Hope that helps.