I've heard that SPL doesn't work as good. I had IPL and I was told from the begining that with face, underarms and brazilian I might need to have more than 6 session, depending on how my body will react.
Now it's been more than 6 months since i've stopped and they haven't grown as yet. Also I was told that I need to get a maintanence every 6 to 12 months. You might have not had that and that's why they're all back.