I had to wear them when I had my left hip replaced. I had to wear them for 3 weeks. Then when I had my right hip replaced I didn't have to wear them. (I had a different doctor) I do think they keep the swelling down some.
Wow, wonder why your Dr says 6 weeks and some of us (like me) didn't have to wear them at all. I did have two of those tests for deep vein problems in the hospital -- maybe that reassures the Dr?