What does varying V Beam pulse width imply?

Hi, I had a consultation with a laser technician the other day and we were discussing Vbeam settings for telengelactasia. I told her that my previous treatments used 6ms with 10.5j settings. She said that we may want to change the pulse width to 10ms. I then asked if that meant we would increase the energy but she said the opposite ie. that energy fluence should decrease. Her rationale was that the longer it "cooks" the less power we need. Is this correct? Thanks.