The PicoSure setting has not been increased after 3 sessions. Should it be if I haven't had frosting since the 1st session?

I have had 3 sessions and i have noticed the practitioner has not increased the power as of yet - it is still saying 300 on the machine. I was informed by someone else at another clinic that they gradually increase the power in stages up to around 700 - 800 as your skin became used to it? is this correct? It doesn't seem to be frosting now like the first two sessions. I'm worried about how long this will take as its costly.