Is it possible to have 6 sessions each of 15 minutes instead of a one hour session?

You are probably not getting cool sculpting.  Those treatments are preset to 1 hour each. You cannot break up the treatments.  

First of all--be sure you are being treated with a Zeltiq Coolsculpting machine. In order for this procedure to work properly it takes one hour with the suction applicators and 2 hours with the Coolsmooth applicator. Anything less will not be effective, and is not an option for proper treatment.