If you don't count pregnancy- I have maintained and even lose with 20-30 minutes 3-4 days per week. I started using The Firm Wave in Jan of this year and with the exception of 1 workout all clocked in at 20-35 minutes. When I didn't feel like using DVDs, I walked (except during the summer due to the extreme heat).
I've been doing 20-35 minute workouts for many, MANY months now, long before pregnancy and not only did I maintain, I lost. Note that I do not "make the minutes count" by working harder or lifting heavier. I go with the flow as to what I want for that day and more often than not, it's not intensity I'm going for. My stress went down by leaps and bounds, I had more energy for daily life, more desire to take on additional projects and hobbies I've been looking forward to, and I have a greater sense of peace and contentment. I think for the most part bc this is a fitness forum, you are not going to find many people that do what I do or are even willing. I took a leap of faith, stumbled many times, but in the end it was well worth the effort to change my mind set, goals, and priorities. It's all about what you want and what will make you happy. It's also about letting go of the control in general but mostly over the vanity that drives so many to workout longer, harder, and/or more often.
But for your original question: YES!