Do you need to permanently use lightening products like Melarase/Nadinola to maintain results?

My buttocks and upper thighs are several shades darker than my overall skin tone. They have not always been this way. The drastic increase in pigmentation happened about four years ago. I am getting great results with 2% and 3% HQ lightening products, but I am concerned about the effects of HQ over a long period of time. After my desired shade in these areas is achieved, can I stop using the lightening product? I am not trying to lighten beyond the skin tone it was before the sudden darkening.