Read David Swenson's reply:
Savasana is an important aspect of the practice. Most of us live incredibly busy and hectic lives. It is wise to take at least a little time at the end of our practice to assimilate the soothing benefits we have accrued during practice.
There are different ideas as to how long one should remain in Savasana. I have a general rule of thumb: Stay at least until the heart rate and breath rate return to a resting rhythm. This may be a different length of time for each student.
As a teacher, it isn't always easy to manage the timing of the class—but that is part of being an effective teacher. We must be aware of the flow and pace of the students in order to save a bit of time at the end to close the class properly. If students want to talk after class, they can always do that outside of the room.
So, as a general answer to your question, I would say that we need to place the same importance on Savasana that we place on all other aspects of the class.
David Swenson made his first trip to Mysore in 1977, learning the full Ashtanga system as originally taught by Sri K. Pattabhi Jois. He is one of the world's foremost instructors of Ashtanga Yoga and has produced numerous videos and DVDs. He is the author of the book Ashtanga Yoga: The Practice Manual.