I think today is filler question day!  If you are using what I call the "mid weight" version - not the Perlane, it generally lasts 4-6 months.  Over time, if you are regular with maintenance, it will even last a little longer sometimes.  A common scenario is 4 months between treatment #1 & #2, 5 months between #2 & #3, and then 6 months between treatment #3 & #4.  You get the picture I think.  The Perlane generally lasts between 6-9 months.   Dr. I